Constraints on signaling of video layers in coded bitstreams

ABSTRACT

A method of video processing includes performing a conversion between a video comprising a plurality of video layers and a bitstream of the video, wherein the bitstream comprises a plurality of output layer sets (OLSs), each of which comprises one or more of the plurality of video layers, and the bitstream conforms to a format rule, wherein the format rule specifies that, for a layer i, where i is an integer, the bitstream includes a set of first syntax element indicative of a first variable indicating whether the layer i is included in at least one of the plurality of OLSs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2020/067016 filed on Dec. 24, 2020, which claims the priorityto and benefits of U.S. Provisional Application No. 62/953,854, filed onDec. 26, 2019, and U.S. Provisional Application No. 62/954,907, filed onDec. 30, 2019. All the aforementioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This patent document relates to image and video coding and decoding.

BACKGROUND

Digital video accounts for the largest bandwidth use on the internet andother digital communication networks. As the number of connected userdevices capable of receiving and displaying video increases, it isexpected that the bandwidth demand for digital video usage will continueto grow.

SUMMARY

The present document discloses techniques that can be used by videoencoders and decoders to perform video encoding or decoding.

In one example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video comprising oneor more scalable video layers and a bitstream of the video. The videocomprises one or more video pictures comprising one or more slices. Thebitstream conforms to a format rule. The format rule specifies that avalue of a field indicative of a slice type of a slice is set toindicate a type of intra slice in case that a corresponding networkabstraction layer unit type is in a predetermined range and that acorresponding video layer flag indicates that a video layercorresponding to the slice does not use inter-layer prediction.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), eachcomprising one or more of the plurality of scalable video layers, andthe bitstream conforms to a format rule,

wherein the format rule specifies that, for an OLS having a singlelayer, a profile-tier-level (PTL) syntax structure that indicates aprofile, a tier and a level for the OLS is included in a video parameterset for the bitstream, and the PTL syntax structure for the OLS is alsoincluded in a sequence parameter set coded in the bitstream.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifies arelationship between occurrence of a number of profile-tier-level (PTL)syntax structures in a video parameter set for the bitstream and a bytealignment syntax field in the video parameter set; wherein each PTLsyntax structure indicates a profile, a tier and a level of one or moreof the plurality of OLS.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video comprising aplurality of scalable video layers and a bitstream of the video, whereinthe bitstream comprises a plurality of output layer sets (OLSs), eachcomprising one or more of the plurality of scalable video layers, andthe bitstream conforms to a format rule, wherein the format rulespecifies that: during encoding, a syntax element indicative of an indexto a syntax structure describing a profile, a tier and a level of one ormore of the plurality of OLSs is excluded from a video parameter set forthe bitstream in case that a value of the index is zero, or, duringdecoding, the value is inferred to be zero in case that the syntaxelement is not present in the bitstream.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifiesthat, for a layer i, where i is an integer, the bitstream includes a setof first syntax element indicative of a first variable indicatingwhether the layer i is included in at least one of the plurality ofOLSs.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video and a bitstreamof the video, wherein the bitstream includes one or more output layersets each comprising one or more video layers; wherein the bitstreamconforms to a format rule, wherein the format rule specifies that anumber of decoded picture buffer parameter syntax structures included ina video parameter set for the bitstream is equal to: zero, in a casethat each output layer set includes a single video layer; or one plus avalue of a syntax element, in a case that each output layer set includesa single layer is not true.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video and a bitstreamof the video, wherein the bitstream includes a coded video sequence(CVS) comprising one or more coded video pictures of one or more videolayers; and wherein the bitstream conforms to a format rule thatspecifies that one or more sequence parameter sets (SPS) indicative ofconversion parameters that are referred to by the one or more codedpictures of the CVS have a same reference video parameter set (VPS)identifier indicative of a referenced VPS.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video and a bitstreamof the video, wherein the bitstream comprises one or more output layersets (OLSs) each comprising one or more video layers, wherein thebitstream conforms to a format rule; wherein the format rule specifieswhether or how a first syntax element indicating whether a first syntaxstructure descriptive of parameters of a hypothetical reference decoder(HRD) used for the conversion is included in a video parameter set (VPS)of the bitstream.

In another example aspect, a video processing method is disclosed. Themethod includes performing a conversion between a video and a bitstreamof the video, wherein the bitstream comprises one or more output layersets (OLSs) each comprising one or more video layers, wherein thebitstream conforms to a format rule; wherein the format rule specifieswhether or how a first syntax structure descriptive of generalhypothetical reference decoder (HRD) parameters and a number of secondsyntax structures descriptive of OLS-specific HRD parameters areincluded in a video parameter set (VPS) for the bitstream.

In yet another example aspect, a video encoder apparatus is disclosed.The video encoder comprises a processor configured to implementabove-described methods.

In yet another example aspect, a video decoder apparatus is disclosed.The video decoder comprises a processor configured to implementabove-described methods.

In yet another example aspect, a computer readable medium having codestored thereon is disclose. The code embodies one of the methodsdescribed herein in the form of processor-executable code.

In yet another example aspect, a method for writing a bitstreamgenerated according to one of the above methods to a computer readablemedium is disclosed.

In another example aspect, a computer readable medium storing abitstream of a video generated according to an above-described method isdisclosed.

These, and other, features are described throughout the presentdocument.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram that illustrates a video coding system inaccordance with some embodiments of the present disclosure.

FIG. 2 is a block diagram of an example hardware platform used for videoprocessing.

FIG. 3 is a flowchart for an example method of video processing.

FIG. 4 is a block diagram that illustrates an example video codingsystem.

FIG. 5 is a block diagram that illustrates an encoder in accordance withsome embodiments of the present disclosure.

FIG. 6 is a block diagram that illustrates a decoder in accordance withsome embodiments of the present disclosure.

FIGS. 7A-7I are flowchart for various video processing method examples.

DETAILED DESCRIPTION

Section headings are used in the present document for ease ofunderstanding and do not limit the applicability of techniques andembodiments disclosed in each section only to that section. Furthermore,H.266 terminology is used in some description only for ease ofunderstanding and not for limiting scope of the disclosed techniques. Assuch, the techniques described herein are applicable to other videocodec protocols and designs also.

1. Summary

This document is related to video coding technologies. Specifically, itis about various improvements in scalable video coding, wherein a videobitstream can contains more than one layer. The ideas may be appliedindividually or in various combination, to any video coding standard ornon-standard video codec that supports multi-layer video coding, e.g.,the being-developed Versatile Video Coding (VVC).

2. Abbreviations

APS Adaptation Parameter Set

AU Access Unit

AUD Access Unit Delimiter

AVC Advanced Video Coding

CLVS Coded Layer Video Sequence

CPB Coded Picture Buffer

CRA Clean Random Access

CTU Coding Tree Unit

CVS Coded Video Sequence

DPB Decoded Picture Buffer

DPS Decoding Parameter Set

EOB End Of Bitstream

EOS End Of Sequence

GDR Gradual Decoding Refresh

HEVC High Efficiency Video Coding

HRD Hypothetical Reference Decoder

IDR Instantaneous Decoding Refresh

JEM Joint Exploration Model

MCTS Motion-Constrained Tile Sets

NAL Network Abstraction Layer

OLS Output Layer Set

PH Picture Header

PPS Picture Parameter Set

PTL Profile, Tier and Level

PU Picture Unit

RBSP Raw Byte Sequence Payload

SEI Supplemental Enhancement Information

SPS Sequence Parameter Set

SVC Scalable Video Coding

VCL Video Coding Layer

VPS Video Parameter Set

VTM VVC Test Model

VUI Video Usability Information

VVC Versatile Video Coding

3. Initial Discussion

Video coding standards have evolved primarily through the development ofthe well-known ITU-T and ISO/IEC standards. The ITU-T produced H.261 andH.263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the twoorganizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4Advanced Video Coding (AVC) and H.265/HEVC [1] standards. Since H.262,the video coding standards are based on the hybrid video codingstructure wherein temporal prediction plus transform coding areutilized. To explore the future video coding technologies beyond HEVC,the Joint Video Exploration Team (JVET) was founded by VCEG and MPEGjointly in 2015. Since then, many new methods have been adopted by JVETand put into the reference software named Joint Exploration Model (JEM)[2]. The JVET meeting is concurrently held once every quarter, and thenew coding standard is targeting at 50% bitrate reduction as compared toHEVC. The new video coding standard was officially named as VersatileVideo Coding (VVC) in the April 2018 JVET meeting, and the first versionof VVC test model (VTM) was released at that time. As there arecontinuous effort contributing to VVC standardization, new codingtechniques are being adopted to the VVC standard in every JVET meeting.The VVC working draft and test model VTM are then updated after everymeeting. The VVC project is now aiming for technical completion (FDIS)at the July 2020 meeting.

3.1. Scalable Video Coding (SVC) in General

Scalable video coding (SVC) refers to video coding in which a base layer(BL), sometimes referred to as a reference layer (RL), and one or morescalable enhancement layers (ELs) are used. In SVC, the base layer cancarry video data with a base level of quality. The one or moreenhancement layers can carry additional video data to support, forexample, higher spatial, temporal, and/or signal-to-noise (SNR) levels.Enhancement layers may be defined relative to a previously encodedlayer. For example, a bottom layer may serve as a BL, while a top layermay serve as an EL. Middle layers may serve as either ELs or RLs, orboth. For example, a middle layer (e.g., a layer that is neither thelowest layer nor the highest layer) may be an EL for the layers belowthe middle layer, such as the base layer or any intervening enhancementlayers, and at the same time serve as a RL for one or more enhancementlayers above the middle layer. Similarly, in the Multiview or 3Dextension of the HEVC standard, there may be multiple views, andinformation of one view may be utilized to code (e.g., encode or decode)the information of another view (e.g., motion estimation, motion vectorprediction and/or other redundancies).

In SVC, the parameters used by the encoder or the decoder are groupedinto parameter sets based on the coding level (e.g., video-level,sequence-level, picture-level, slice level, etc.) in which they may beutilized. For example, parameters that may be utilized by one or morecoded video sequences of different layers in the bitstream may beincluded in a video parameter set (VPS), and parameters that areutilized by one or more pictures in a coded video sequence may beincluded in a sequence parameter set (SPS). Similarly, parameters thatare utilized by one or more slices in a picture may be included in apicture parameter set (PPS), and other parameters that are specific to asingle slice may be included in a slice header. Similarly, theindication of which parameter set(s) a particular layer is using at agiven time may be provided at various coding levels.

3.2. Parameter Sets

AVC, HEVC, and VVC specify parameter sets. The types of parameter setsinclude SPS, PPS, APS, VPS, and DPS. SPS and PPS are supported in all ofAVC, HEVC, and VVC. VPS was introduced since HEVC and is included inboth HEVC and VVC. APS and DPS were not included in AVC or HEVC, but areincluded in the latest VVC draft text.

SPS was designed to carry sequence-level header information, and PPS wasdesigned to carry infrequently changing picture-level headerinformation. With SPS and PPS, infrequently changing information neednot to be repeated for each sequence or picture, hence redundantsignalling of these information can be avoided. Furthermore, the use ofSPS and PPS enables out-of-b and transmission of the important headerinformation, thus not only avoiding the need for redundant transmissionsbut also improving error resilience.

VPS was introduced for carrying sequence-level header information thatis common for all layers in multi-layer bitstreams.

APS was introduced for carrying such picture-level or slice-levelinformation that needs quite some bits to code, can be shared bymultiple pictures, and in a sequence there can be quite many differentvariations.

DPS was introduced for carrying bitstream-level information thatindicates the highest capability needed for decoding the entirebitstream.

3.3. VPS Syntax and Semantics in VVC

VVC supports scalability, also known as scalable video coding, whereinmultiple layers can be encoded in one coded video bitstream.

In the latest VVC text, the scalability information is signalled in theVPS, the syntax and semantics are as follows.

7.3.2.2 Video Parameter Set Syntax

Descriptor video_parameter_set_rbsp( ) {  vps_video_parameter_set_idu(4)  vps_max_layers_minus1 u(6)  vps_max_sublayers_minus1 u(3)  if(vps_max_layers_minus1 > 0 && vps_max_sublayers_minus1 > 0 )  vps_all_layers_same_num_sublayers_flag u(1)  if(vps_max_layers_minus1 > 0 )   vps_all_independent_layers_flag u(1)  for(i = 0; i <= vps_max_layers_minus1; i++ ) {   vps_layer_id[ i ] u(6)  if( i > 0 && !vps_all_independent_layers_flag ) {   vps_independent_layer_flag[ i ] u(1)    if(!vps_independent_layer_flag[ i ] )     for(j = 0; j < i; j++ )     vps_direct_ref_layer_flag[ i ][ j ] u(1)   }  }  if(vps_max_layers_minus1 > 0 ) {   if( vps_all_independent_layers_flag )   each_layer_is_an_ols_flag u(1)   if( !each_layer_is_an_ols_flag ) {   if( !vps_all_independent_layers_flag )     ols_mode_idc u(2)    if(ols_mode_idc == 2 ) {     num_output_layer_sets_minus1 u(8)     for( i =1; i <= num_output_layer_sets_minus1; i++)      for(j = 0; j <=vps_max_layers_minus1; j++ )       ols_output_layer_flag[ i ][ j ] u(1)   }   }  }  vps_num_ptls u(8)  for( i = 0; i < vps_num_ptls; i++ ) {  if( i > 0 )    pt_present_flag[ i ] u(1)   if(vps_max_sublayers_minus1 > 0 && !vps_all_layers_same_num_sublayers_flag)    ptl_max_temporal_id[ i ] u(3)  }  while( !byte_aligned( ) )  vps_ptl_byte_alignment_zero_bit /* equal to 0 */ u(1)  for( i = 0; i <vps_num_ptls; i++ )   profile_tier_level( pt_present_flag[ i ],ptl_max_temporal_id[ i] )  for( i = 0; i < TotalNumOlss; i++ )   if(NumLayersInOls[ i ] > 1 && vps_num_ptls> 1 )    ols_ptl_idx[ i ] u(8) if( !vps_all_independent_layers_flag )   vps_num_dpb_params ue(v)  if(vps_num_dpb_params > 0 ) {   same_dpb_size_output_or_nonoutput_flag u(1)  if( vps_max_sublayers_minus1 > 0 )   vps_sublayer_dpb_params_present_flag u(1)  }  for( i = 0; i <vps_num_dpb_params; i++ ) {   dpb_size_only_flag[ i ] u(1)   if(vps_max_sublayers_minus1 > 0 && !vps_all_layers_same_num_sublayers_flag)    dpb_max_temporal_id[ i ] u(3)   dpb_parameters( dpb_size_only_flag[i ], dpb_max_temporal_id[ i ],      vps_sublayer_dpb_params_present_flag )  }  for( i = 0; i <vps_max_layers_minus1 && vps_num_dpb_params > 1; i++ ) {   if(!vps_independent_layer_flag[ i ] )    layer_output_dpb_params_idx[ i ]ue(v)   if( LayerUsedAsRefLayerFlag[ i ] &&!same_dpb_size_output_or_nonoutput_flag )   layer_nonoutput_dpb_params_idx[ i ] ue(v)  } vps_general_hrd_params_present_flag u(1)  if(vps_general_hrd_params_present_flag ) {   general_hrd_parameters( )  if( vps_max_sublayers_minus1 > 0 )   vps_sublayer_cpb_params_present_flag u(1)   if( TotalNumOlss > 1 )   num_ols_hrd_params_minus1 ue(v)   for( i = 0; i <=num_ols_hrd_params_minus1; i++ ) {    if( vps_max_sublayers_minus1 > 0&& !vps_all_layers_same_num_sublayers_flag )     hrd_max_tid[ i ] u(3)   firstSubLayer = vps_sublayer_cpb_params_present_flag? 0 :hrd_max_tid[ i ]    ols_hrd_parameters( firstSubLayer,hrd_max_temporal_id[ i ] )   }   if( num_ols_hrd_params_minus1 > 0 )   for( i = 1; i < TotalNumOlss; i++ )     ols_hrd_idx[ i ] ue(v)  } vps_extension_flag u(1)  if( vps_extension_flag )   while(more_rbsp_data( ) )    vps_extension_data_flag u(1)  rbsp_trailing_bits( ) }7.4.3.2 Video Parameter Set RBSP SemanticsA VPS RBSP shall be available to the decoding process prior to it beingreferenced, included in at least one AU with TemporalId equal to 0 orprovided through external means.All VPS NAL units with a particular value of vps_video_parameter_set_idin a CVS shall have the same content.vps_video_parameter_set_id provides an identifier for the VPS forreference by other syntax elements. The value ofvps_video_parameter_set_id shall be greater than 0.vps_max_layers_minus1 plus 1 specifies the maximum allowed number oflayers in each CVS referring to the VPS.vps_max_sublayers_minus1 plus 1 specifies the maximum number of temporalsublayers that may be present in each CVS referring to the VPS. Thevalue of vps_max_sublayers_minus1 shall be in the range of 0 to 6,inclusive.vps_all_layers_same_num_sublayers_flag equal to 1 specifies that thenumber of temporal sublayers is the same for all the layers in each CVSreferring to the VPS. vps_all_layers_same_num_sublayers_flag equal to 0specifies that the layers in each CVS referring to the VPS may or maynot have the same number of temporal sublayers. When not present, thevalue of vps_all_layers_same_num_sublayers_flag is inferred to be equalto 1.vps_all_independent_layers_flag equal to 1 specifies that all layers inthe CVS are independently coded without using inter-layer prediction.vps_all_independent_layers_flag equal to 0 specifies that one or more ofthe layers in the CVS may use inter-layer prediction. When not present,the value of vps_all_independent_layers_flag is inferred to be equalto 1. When vps_all_independent_layers_flag is equal to 1, the value ofvps_independent_layer_flag[i] is inferred to be equal to 1. Whenvps_all_independent_layers_flag is equal to 0, the value ofvps_independent_layer_flag[0] is inferred to be equal to 1.vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer. Forany two non-negative integer values of m and n, when m is less than n,the value of vps_layer_id[m] shall be less than vps_layer_id[n].vps_independent_layer_flag[i] equal to 1 specifies that the layer withindex i does not use inter-layer prediction.vps_independent_layer_flag[i] equal to 0 specifies that the layer withindex i may use inter-layer prediction and the syntax elementsvps_direct_ref_layer_flag[i][j] for j in the range of 0 to i−1,inclusive, are present in VPS. When not present, the value ofvps_independent_layer_flag[i] is inferred to be equal to 1.vps_direct_ref_layer_flag[i][j] equal to 0 specifies that the layer withindex j is not a direct reference layer for the layer with index i.vps_direct_ref_layer_flag [i][j] equal to 1 specifies that the layerwith index j is a direct reference layer for the layer with index i.When vps_direct_ref_layer_flag[i][j] is not present for i and j in therange of 0 to vps_max_layers_minus1, inclusive, it is inferred to beequal to 0. When vps_independent_layer_flag[i] is equal to 0, thereshall be at least one value of j in the range of 0 to i−1, inclusive,such that the value of vps_direct_ref_layer_flag[i][j] is equal to 1.The variables NumDirectRefLayers[i], DirectRefLayerIdx[i][d],NumRefLayers[i], RefLayerIdx[i][r], and LayerUsedAsRefLayerFlag[j] arederived as follows:

for( i = 0; i <= vps_max_layers_minus1; i++ ) (37)  for( j = 0; j <=vps_max_layers_minus1; j++ ) {   dependencyFlag[ i ][ j ] =vps_direct_ref_layer_flag[ i ][ j ]   for( k = 0; k < i; k++ )    if(vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] )    dependencyFlag[ i ][ j ] = 1  } for( i = 0; i <=vps_max_layers_minus1; i++ ) {  LayerUsedAsRefLayerFlag[ j ] = 0  for( j= 0, d = 0, r = 0; j <= vps_max_layers_minus1; j++ ) {   if(direct_ref_layer_flag[ i ][ j ] ) {    DirectRefLayerIdx[ i ][ d++ ] = j   LayerUsedAsRefLayerFlag[ j ] = 1   }   if( dependencyFlag[ i ][ j ] )   RefLayerIdx[ i ][ r++ ] = j  }  NumDirectRefLayers[ i ] = d NumRefLayers[ i ] = r }The variable GeneralLayerIdx[i], specifying the layer index of the layerwith nuh_layer_id equal to vps_layer_id[i], is derived as follows:

for( i = 0; i <= vps_max_layers_minus1; i++ ) (38)  GeneralLayerIdx[vps_layer_id[ i ] ] = ieach_layer_is_an_ols_flag equal to 1 specifies that each output layerset contains only one layer and each layer itself in the bitstream is anoutput layer set with the single included layer being the only outputlayer. each_layer_is_an_ols_flag equal to 0 that an output layer set maycontain more than one layer. If vps_max_layers_minus1 is equal to 0, thevalue of the value of each_layer_is_an_ols_flag is inferred to be equalto 1. Otherwise, when vps_all_independent_layers_flag is equal to 0, thevalue of each_layer_is_an_ols_flag is inferred to be equal to 0.ols_mode_idc equal to 0 specifies that the total number of OLSsspecified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLSincludes the layers with layer indices from 0 to i, inclusive, and foreach OLS only the highest layer in the OLS is output.ols_mode_idc equal to 1 specifies that the total number of OLSsspecified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLSincludes the layers with layer indices from 0 to i, inclusive, and foreach OLS all layers in the OLS are output.ols_mode_idc equal to 2 specifies that the total number of OLSsspecified by the VPS is explicitly signalled and for each OLS the outputlayers are explicitly signalled and other layers are the layers that aredirect or indirect reference layers of the output layers of the OLS.The value of ols_mode_idc shall be in the range of 0 to 2, inclusive.The value 3 of ols_mode_idc is reserved for future use by ITU-T|ISO/IEC.When vps_all_independent_layers_flag is equal to 1 andeach_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc isinferred to be equal to 2.num_output_layer_sets_minus1 plus 1 specifies the total number of OLSsspecified by the VPS when ols_mode_idc is equal to 2.The variable TotalNumOlss, specifying the total number of OLSs specifiedby the VPS, is derived as follows:

if( vps_max_layers_minus1 == 0 ) (39)  TotalNumOlss = 1 else if(each_layer_is_an_ols_flag || ols_mode_idc == 0 || ols_mode_idc == 1 ) TotalNumOlss = vps_max_layers_minus1 + 1 else if( ols_mode_idc == 2 ) TotalNumOlss = num_output_layer_sets_minus1 + 1ols_output_layer_flag[i][j] equal to 1 specifies that the layer withnuh_layer_id equal to vps_layer_id[j] is an output layer of the i-th OLSwhen ols_mode_idc is equal to 2. ols_output_layer_flag[i][j] equal to 0specifies that the layer with nuh_layer_id equal to vps_layer_id[j] isnot an output layer of the i-th OLS when ols_mode_idc is equal to 2.The variable NumOutputLayersInOls[i], specifying the number of outputlayers in the i-th OLS, and the variable OutputLayerIdInOls[i][j],specifying the nuh_layer_id value of the j-th output layer in the i-thOLS, are derived as follows:

NumOutputLayersInOls[ 0 ] = 1 (40) OutputLayerIdInOls[ 0 ][ 0 ] =vps_layer_id[ 0 ] for( i = 1; i < TotalNumOlss; i++ ) {  if(each_layer_is_an_ols_flag || ols_mode_idc == 0 ) {  NumOutputLayersInOls[ i ] = 1   OutputLayerIdInOls[ i ][ 0 ] =vps_layer_id[ i ]  } else if( ols_mode_idc == 1 ) {  NumOutputLayersInOls[ i ] = i + 1   for( j = 0; j <NumOutputLayersInOls[ i ]; j++ )    OutputLayerIdInOls[ i ][ j ] =vps_layer_id[ j ]  } else if( ols_mode_idc == 2) {   for( j = 0; j <=vps_max_layers_minus1; j++ )    layerIncludedFlag[ i ][ j ] = 0   for( k= 0, j = 0; k <= vps_max_layers_minus1; k++ )    if(ols_output_layer_flag[ i ][ k ] ) {     layerIncludedFlag[ i ][ j ] = 1    OutputLayerIdx[ i ][ j ] = k     OutputLayerIdInOls[ i ][ j++ ] =vps_layer_id[ k ]    }   NumOutputLayersInOls[ i ] = j   for( j = 0; j >NumOutputLayersInOls[ i ]; j++ ) {    idx = OutputLayerIdx[ i ][ j ]   for( k = 0; k < NumRefLayers[ idx ]; k++ )     layerIncludedFlag[ i][ RefLayerIdx[ idx ][ k ] ] = 1   }  } }For each OLS, there shall be at least one layer that is an output layer.In other words, for any value of i in the range of 0 to TotalNumOlss−1,inclusive, the value of NumOutputLayersInOls[i] shall be greater than orequal to 1.The variable NumLayersInOls[i], specifying the number of layers in thei-th OLS, and the variable LayerIdInOls[i][j], specifying thenuh_layer_id value of the j-th layer in the i-th OLS, are derived asfollows:

NumLayersInOls[ 0 ] = 1 (41) LayerIdInOls[ 0 ][ 0 ] = vps_layer_id[ 0 ]for( i = 1; i < TotalNumOlss; i++ ) {  if( each_layer_is_an_ols_flag ) {  NumLayersInOls[ i ] = 1   LayerIdInOls[ i ][ 0 ] = vps_layer_id[ i ] } else if( ols_mode_idc == 0 || ols_mode_idc == 1 ) {   NumLayersInOls[i ] = i + 1   for( j = 0; j < NumLayersInOls[ i ]; j++ )   LayerIdInOls[ i ][ j ] = vps_layer_id[ j ]  } else if( ols_mode_idc== 2 ) {   for( k = 0, j = 0; k <= vps_max_layers_minus1; k++ )    if(layerIncludedFlag[ i ][ k ] )     LayerIdInOls[ i ][ j++ ] =vps_layer_id[ k ]   NumLayersInOls[ i ] = j  } }

-   -   NOTE 1—The 0-th OLS contains only the lowest layer (i.e., the        layer with nuh_layer_id equal to vps_layer_id[0]) and for the        0-th OLS the only included layer is output.        The variable OlsLayerIdx[i][j], specifying the OLS layer index        of the layer with nuh_layer_id equal to LayerIdInOls[i][j], is        derived as follows:

for( i = 0; i < TotalNumOlss; i++ ) (42)  for j = 0; j < NumLayersInOls[i ]; j++ )   OlsLayeIdx[ i ][ LayerIdInOls[ i ][ j ] ] = jThe lowest layer in each OLS shall be an independent layer. In otherwords, for each i in the range of 0 to TotalNumOlss−1, inclusive, thevalue of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]]shall be equal to 1.Each layer shall be included in at least one OLS specified by the VPS.In other words, for each layer with a particular value of nuh_layer_idnuhLayerId, equal to one of vps_layer_id[k] for k in the range of 0 tovps_max_layers_minus1, inclusive, there shall be at least one pair ofvalues of i and j, where i is in the range of 0 to TotalNumOlss−1,inclusive, and j is in the range of NumLayersInOls[i]−1, inclusive, suchthat the value of LayerIdInOls[i][j] is equal to nuhLayerId.vps_num_ptls specifies the number of profile_tier_level( ) syntaxstructures in the VPS.pt_present_flag[i] equal to 1 specifies that profile, tier, and generalconstraints information are present in the i-th profile_tier_level( )syntax structure in the VPS. pt_present_flag[i] equal to 0 specifiesthat profile, tier, and general constraints information are not presentin the i-th profile_tier_level( ) syntax structure in the VPS. The valueof pt_present_flag[0] is inferred to be equal to 0. Whenpt_present_flag[i] is equal to 0, the profile, tier, and generalconstraints information for the i-th profile_tier_level( ) syntaxstructure in the VPS are inferred to be the same as that for the(i−1)-th profile_tier_level( ) syntax structure in the VPS.ptl_max_temporal_id[i] specifies the TemporalId of the highest sublayerrepresentation for which the level information is present in the i-thprofile_tier_level( ) syntax structure in the VPS. The value ofptl_max_temporal_id[i] shall be in the range of 0 tovps_max_sublayers_minus1, inclusive. When vps_max_sublayers_minus1 isequal to 0, the value of ptl_max_temporal_id[i] is inferred to be equalto 0. When vps_max_sublayers_minus1 is greater than 0 andvps_all_layers_same_num_sublayers_flag is equal to 1, the value ofptl_max_temporal_id[i] is inferred to be equal tovps_max_sublayers_minus1.vps_ptl_byte_alignment_zero_bit shall be equal to 0.ols_ptl_idx[i] specifies the index, to the list of profile_tier_level( )syntax structures in the VPS, of the profile_tier_level( ) syntaxstructure that applies to the i-th OLS. When present, the value ofols_ptl_idx[i] shall be in the range of 0 to vps_num_ptls−1, inclusive.When NumLayersInOls[i] is equal to 1, the profile_tier_level( ) syntaxstructure that applies to the i-th OLS is present in the SPS referred toby the layer in the i-th OLS.vps_num_dpb_params specifies the number of dpb_parameters( ) syntaxstructures in the VPS. The value of vps_num_dpb_params shall be in therange of 0 to 16, inclusive. When not present, the value ofvps_num_dpb_params is inferred to be equal to 0.same_dpb_size_output_or_nonoutput_flag equal to 1 specifies that thereis no layer_nonoutput_dpb_params_idx[i] syntax element present in theVPS. same_dpb_size_output_or_nonoutput_flag equal to 0 specifies thatthere mas or may not be layer_nonoutput_dpb_params_idx[i] syntaxelements present in the VPSvps_sublayer_dpb_params_present_flag is used to control the presence ofmax_dec_pic_buffering_minus1[ ]. max_num_reorder_pics[ ]. andmax_latency_increase_plus1[ ] syntax elements in the dpb_parameters( )syntax structures in the VPS. When not presentvps_sub_dpb_params_info_present_flag is inferred to be equal to 0.dpb_size_only_flag[i] equal to 1 specifies that themax_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntaxelements are not present in the i-th dpb_parameters( ) syntax structuresthe VPS. dpb_size_only_flag[i] equal to 1 specifies that themax_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntaxelements may be present in the i-th dpb_parameters( ) syntax structuresthe VPS.dpb_max_temporal_id[i] specifies the TemporalId of the highest sublayerrepresentation for which the DPB parameters may be present in the i-thdpb_parameters( ) syntax structure in the VPS. The value ofdpb_max_temporal_id[i] shall be in the range of 0 tovps_max_sublayers_minus1, inclusive. When vps_max_sublayers_minus1 isequal to 0, the value of dpb_max_temporal_id[i] is inferred to be equalto ( ). When vps_max_sublayers_minus1 is greater than 0 andvps_all_layers_same_num_sublayers_flag is equal to 1, the value ofdpb_max_temporal_id[i] is inferred to be equal tovps_max_sublayers_minus1.layer_output_dpb_params_idx[i] specifies the index, to the list ofdpb_parameters( ) syntax structures in the VPS. of the dpb_parameters( )syntax structure that applies to the i-th layer when it is an outputlayer in an OLS. When present, the value oflayer_output_dpb_params_idx[i] shall be in the range of 0 tovps_num_dpb_params−1, inclusive.If vps_independent_layer_flag[i] is equal to 1, the dpb_parameters( )syntax structure that applies to the i-th layer when it is an outputlayer is the dpb_parameters( ) syntax structure present in the SPSreferred to by the layer.Otherwise (vps_independent_layer_flag[i] is equal to 0), the followingapplies:

-   -   When vps_num_dpb_params is equal to 1. the value of        layer_output_dpb_params_idx[i] is inferred to be equal to 0.    -   It is a requirement of bitstream conformance that the value of        layer_output_dpb_params_idx[i] shall be such that        dpb_size_only_flag[layer_output_dpb_params_idx[i]] is equal to        0.        layer_nonoutput_dpb_params_idx[i] specifies the index, to the        list of dpb_parameters( ) syntax structures in the VPS, of the        dpb_parameters( ) syntax structure that applies to the i-th        layer when it is a non-output layer in an OLS. When present, the        value of layer_nonoutput_dpb_params_idx[i] shall be in the range        of 0 to vps_num_dpb_params−1, inclusive.        If same_dpb_size_output_or_nonoutput_flag is equal to 1. the        following applies:    -   If vps_independent_layer_flag[i] is equal to 1, the        dpb_parameters( ) syntax structure that applies to the i-th        layer when it is a non-output layer is the dpb_parameters( )        syntax structure present in the SPS referred to by the layer.    -   Otherwise (vps_independent_layer_flag[i] is equal to 0), the        value of layer_nonoutput_dpb_params_idx[i] is inferred to be        equal to layer_output_dpb_params_idx[i].        Otherwise (same dpb_size_output_or_nonoutput_flag is equal to        0), when vps_num_dpb_params is equal to 1, the value of        layer_output_dpb_params_idx[i] is inferred to be equal to 0.        vps_general_hrd_params_present_flag equal to 1 specifies that        the syntax structure general_hrd_parameters( ) and other HRD        parameters are present in the VPS RBSP syntax structure        vps_general_hrd_params_present_flag equal to 0 specifies that        the syntax structure general_hrd_parameters( ) and other HRD        parameters are not present in the VPS RBSP syntax structure.        vps_sublayer_cpb_params_present_flag equal to 1 specifies that        the i-th ols_hrd_parameters( ) syntax structure in the VPS        contains HRD parameters for the sublayer representations with        Temporal Id in the range of 0 to hrd_max_tid[i], inclusive.        vps_sublayer_cpb_params_present_flag equal to 0 specifies that        the i-th ols_hrd_parameters( ) syntax structure in the VPS        contains HRD parameters for the sublayer representation with        TemporalId equal to hrd_max_tid[i] only. When        vps_max_sublayers_minus1 is equal to 0, the value of        vps_sublayer_cpb_params_present_flag is inferred to be equal to        0.        When vps_sublayer_cpb_params_present_flag is equal to 0, the HRD        parameters for the sublayer representations with TemporalId in        the range of 0 to hrd_max_tid[i]−1, inclusive, are inferred to        be the same as that for the sublayer representation with        TemporalId equal to hrd_max_tid[i]. These include the HRD        parameters starting from the fixed_pic_rate_general_flag[i]        syntax element till the sublayer_hrd_parameters(i) syntax        structure immediately under the condition        “if(general_vcl_hrd_params_present_flag)” in the        ols_hrd_parameters syntax structure.        num_ols_hrd_params_minus1 plus 1 specifies the number of        ols_hrd_parameters( ) syntax structures present in the        general_hrd_parameters( ) syntax structure. The value of        num_ols_hrd_params_minus1 shall be in the range of 0 to 63,        inclusive. When TotalNumOlss is greater than 1, the value of        num_ols_hrd_params_minus1 is inferred to be equal to 0.        hrd_max_tid[i] specifies the TemporalId of the highest sublayer        representation for which the HRD parameters are contained in the        i-th ols_hrd_parameters( ) syntax structure. The value of        hrd_max_tid[i] shall be in the range of 0 to        vps_max_sublayers_minus1, inclusive. When        vps_max_sublayers_minus1 is equal to 0, the value of        hrd_max_tid[i] is inferred to be equal to 0.        ols_hrd_idx[i] specifies the index of the ols_hrd_parameters( )        syntax structure that applies to the i-th OLS. The value of        ols_hrd_idx[[i] shall be in the range of 0 to        num_ols_hrd_params_minus1, inclusive. When not present, the        value of ols_hrd_idx[[i] is inferred to be equal to 0.        vps_extension_flag equal to 0 specifies that no        vps_extension_data_flag syntax elements are present in the VPS        RBSP syntax structure. vps_extension_flag equal to 1 specifies        that there are vps_extension_data_flag syntax elements present        in the VPS RBSP syntax structure.        vps_extension_data_flag may have any value. Its presence and        value do not affect decoder conformance to profiles specified in        this version of this Specification. Decoders conforming to this        version of this Specification shall ignore all        vps_extension_data_flag syntax elements.        3.4. SPS Syntax and Semantics in VVC

In the latest VVC draft text in WET-P2001-v14, the SPS syntax andsemantics that are most relevant to the inventions herein are asfollows.

7.3.2.3 Sequence Parameter Set RBSP Syntax

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4)  sps_video_parameter_set_id u(4)  sps_max_sublayers_minus1 u(3) sps_reserved_zero_4bits u(4)  sps_ptl_dpb_hrd_params_present_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag )   profile_tier_level( 1,sps_max_sublayers_minus1 )  . . .7.4.3.3 Sequence Parameter Set RBSP SemanticsAn SPS RBSP shall be available to the decoding process prior to it beingreferenced, included in at least one AU with TemporalId equal to 0 orprovided through external means.All SPS NAL units with a particular value of sps_seq_parameter_set_id ina CVS shall have the same content.sps_decoding_parameter_set_id. when greater than 0, specifies the valueof dps_decoding_parameter_set_id for the DPS referred to by the SPS.When sps_decoding_parameter_set_id is equal to 0, the SPS does not referto a DPS and no DPS is referred to when decoding each CLVS referring tothe SPS. The value of sps_decoding_parameter_set_id shall be the same inall SPSs that are referred to by coded pictures in a bitstream.sps_video_parameter_set_id, when greater than 0, specifies the value ofvps_video_parameter_set_id for the VPS referred to by the SPS.When sps_video_parameter_set_id is equal to 0. the following applies:

-   -   The SPS does not refer to a VPS.    -   No VPS is referred to when decoding each CLVS referring to the        SPS.    -   The value of vps_max_layers_minus1 is inferred to be equal to 0.    -   The CVS shall contain only one layer (i.e., all VCL NAL unit in        the CVS shall have the same value of nuh_layer_id).    -   The value of GeneralLayerIdx[nuh_layer_id] is inferred to be        equal to 0.    -   The value of        vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is        inferred to be equal to 1.        When vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]        is equal to 1. the SPS referred to by a CLVS with a particular        nuh_layer_id value nuhLayerId shall have nuh_layer_id equal to        nuhLayerId.        sps_max_sublayers_minus1 plus 1 specifies the maximum number of        temporal sublayers that may be present in each CLVS referring to        the SPS. The value of sps_max_sublayers_minus1 shall be in the        range of 0 to vps_max_sublayers_minus1. inclusive.        sps_reserved_zero_4 bits shall be equal to 0 in bitstreams        conforming to this version of this Specification. Other values        for sps_reserved_zero_4 bits are reserved for future use by        ITU-T|ISO/IEC.        sps_ptl_dpb_hrd_params_present_flag equal to 1 specifies that a        profile_tier_level( ) syntax structure and a dpb_parameters( )        syntax structure are present in the SPS. and a        general_hrd_parameters( ) syntax structure and an        ols_hrd_parameters( ) syntax structure may also be present in        the SPS sps_ptl_dpb_hrd_params_present_flag equal to 0 specifies        that none of these syntax structures is present in the SPS. The        value of sps_ptl_dpb_hrd_params_present_flag shall be equal to        vps_independent_layer_flag[nuh_layer_id].        If vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is        equal to 1, the variable MaxDecPicBuffMinus1 is set equal to        max_dec_pic_buffering_minus1[sps_max_sublayers_minus1] in the        dpb_parameters( ) syntax structure in the SPS Otherwise.        MaxDecPicBuffMinus1 is set equal to        max_dec_pic_buffering_minus1[sps_max_sublayers_minus1] in the        layer_nonoutput_dpb_params_idx[GeneralLayerIdx[nuh_layer_id]]-th        dpb_parameters( ) syntax structure in the VPS.        3.5. Slice Header Syntax and Semantics in VVC

In the latest VVC draft text in JVET-P2001-v14, the slice header syntaxand semantics that are most relevant to the inventions herein are asfollows.

7.3.7.1 General Slice Header Syntax

Descriptor slice_header( ) {  slice_pic_order_cnt_lsb u(v)  if(subpics_present_flag )   slice_subpic_id u(v)  if( rect_slice_flag ||NumTilesInPic > 1 )   slice_address u(v)  if( !rect_slice_flag &&NumTilesInPic > 1 )   num_tiles_in_slice_minus1 ue(v)  slice_type ue(v). . .7.4.8.1 General Slice Header Semanticsslice_type specifies the coding type of the slice according to Table 9.

TABLE 9 Name association to slice_type slice_type Name of slice_type 0 B(B slice) 1 P (P slice) 2 I (I slice)When nal_unit_type is a value of nal_unit_type in the range ofIDR_W_RADL to CRA_NUT, inclusive, and the current picture is the firstpicture in an access unit, slice type shall be equal to 2.

4. Technical Problems Solved by Described Technical Solutions

The existing scalability design in VVC has the following problems:

-   -   1) The latest VVC draft text includes the following constraint        on slice type:        -   When nal_unit_type is a value of nal_unit_type in the range            of IDR_W_RADL to CRA_NUT, inclusive, and the current picture            is the first picture in an AU, slice type shall be equal to            2.        -   The value of slice_type equal to 2 for a slice means that            the slice is intra coded without using inter prediction from            a reference picture.        -   However, in an AU, not only the first picture that is in the            AU and that is an TRAP picture needs to contain intra-coded            slices only, but also all the TRAP pictures in all the            independent layers need to contain intra-coded slices only.            Therefore, the above constraint does needs to be updated.    -   2) When the syntax element ols_ptl_idx[i] is not present, the        value still needs to be used. However, there lacks an inference        of the value of ols_ptl_idx[i] when it is not present.    -   3) The signalling of the syntax element        layer_output_dpb_params_idx[i] is unnecessary when the i-layer        is not used as an output layer in any of the OLSs.    -   4) The value of the syntax element vps_num_dpb_params can be        equal to 0. However, there needs to be at least one        dpb_parameters( ) syntax structure in the VPS when        vps_all_independent_layers_flag is equal to 0.    -   5) In the latest VVC draft text, the PTL information for OLSs        containing only one layer, such a layer is an independently        coded layer without referring to any other layer, is only        signalled in the SPS. However, it would be desirable to signal        the PTL information for all OLSs in a bitstream in the VPS for        session negotiation purposes.    -   6) The vps_ptl_byte_alignment_zero_bit syntax element is        unnecessarily signalled when the number of PTL syntax structures        signalled in the VPS is zero.    -   7) In the semantics of sps_video_parameter_set_id, there is the        following constraint:        -   When sps_video_parameter_set_id is equal to 0, the CVS shall            contain only one layer (i.e., all VCL NAL unit in the CVS            shall have the same value of nuh_layer_id).        -   However, this constraint disallows an independent layer that            does not refer to a VPS to be included in a multi-layer            bitstream. As sps_video_parameter_set_id equal to 0 means            that the SPS (and the layer) does not refer to a VPS.    -   8) The value of vps_general_hrd_params_present_flag can be equal        to 1 when each_layer_is_an_ols_flag is equal to 1. However, when        each_layer_is_an_ols_flag is equal to 1, the HRD parameters are        only signalled in the SPSs, therefore the value of        vps_general_hrd_params_present_flag shall not be equal to 1. In        some cases, it may not make sense to signal the        general_hrd_parameter( ) syntax structure while signaling zero        old_hrd_parameters( ) syntax structures in the VPS.    -   9) The HRD parameters for OLSs containing only one layer are        signalled in both the VPS and the SPSs. However, it is not        useful to repeat the HRD parameters in the VPS for OLSs        containing only one layer.

5. Example Embodiments and Techniques

To solve the above problems, and others, methods as summarized below aredisclosed. The inventions should be considered as examples to explainthe general concepts and should not be interpreted in a narrow way.Furthermore, these inventions can be applied individually or combined inany manner.

-   -   1) To solve the first problem, the following constraint is        specified:        -   When nal_unit_type is in the range of IDR_W_RADL to CRA_NUT,            inclusive, and            vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is            equal to 1, slice type shall be equal to 2.    -   2) To solve the second problem, for each value of possible value        of i, the value of ols_ptl_idx[i] is inferred to be equal to 0        when the syntax element is not present.    -   3) To solve the third problem, the variable        LayerUsedAsOutputLayerFlag[i] is specified to indicate whether        the i-layer is used as an output layer in whichever OLS, and        when the variable is equal to 0, the signalling of the variable        layer_output_dpb_params_idx[i] is avoided.        -   a. Furthermore, the following constraint may be additionally            specified: For each value of i in the range of 0 to            vps_max_layers_minus1, inclusive, the values of            LayerUsedAsRefLayerFlag[i] and LayerUsedAsOutputLayerFlag[i]            shall not be both equal to 0. In other words, there shall be            no layer that is neither a direct reference layer of any            other layer nor an output layer of at least one OLS.    -   4) To solve the fourth problem, change vps_num_dpb_params to        vps_num_dpb_params_minus1, and specify VpsNumDpbParams as        follows:

  if( !vps_all_independent_layers_flag )  VpsNumDpbParams =vps_num_dpb_params_minus1 + 1 else  VpsNumDpbParams = 0

-   -   -   And replace the use of vps_num_dpb_params in the syntax            conditions and the semantics with VpsNumDpbParams.        -   a. Furthermore, the following constraint is additionally            specified: When not present, the value of            same_dpb_size_output_or_nonoutput_flag is inferred to be            equal to 1.

    -   5) To solve the fifth problem, allow repeating in the VPS the        PTL information for OLSs containing only one layer for session        negotiation purposes. This can be realized by changing        vps_num_ptls to vps_num_ptls_minus1.        -   a. Alternatively, keep vps_num_ptls (without making it            vps_num_ptls_minus1), but remove“NumLayersInOls[i]>1 &&”            from the syntax condition for ols_ptl_idx[i].        -   a. Alternatively, keep vps_num_ptls (without making it            vps_num_ptls_minus1), but condition vps_num_ptls on            “if(!each_layer_is_an_ols_flag )”, or            “if(vps_max_layers_minus1>0 &&            !vps_all_independent_layers_flag”.        -   b. Alternatively, also allow repeating the DPB parameters            information (either just the DPB size or all DPB parameters)            for OLSs containing only one layer in the VPS.

    -   6) To solve the sixth problem, the        vps_ptl_byte_alignment_zero_bit syntax element is not signalled        as long as the number of PTL syntax structures signalled in the        VPS is zero. This can be realized by additionally conditioning        vps_ptl_byte_alignment_zero_bit on “if(vps_num_ptls>0)” or by        changing vps_num_ptls to vps_num_ptls_minus1, which effectively        disallows the number of PTL syntax structures signalled in the        VPS to be equal to zero.

    -   7) To solve the seventh problem, remove the following        constraint:        -   When sps_video_parameter_set_id is equal to 0, the CVS shall            contain only one layer (i.e., all VCL NAL unit in the CVS            shall have the same value of nuh_layer_id).        -   And add the following constraint:        -   The value of sps_video_parameter_set_id shall be the same in            all SPSs that are referred to by coded pictures in a CVS and            that have sps_video_parameter_set_id greater than 0.            -   a. Alternatively, keep the following constraint:                -   When sps_video_parameter_set_id is equal to 0, the                    CVS shall contain only one layer (i.e., all VCL NAL                    unit in the CVS shall have the same value of                    nuh_layer_id).            -   And specify the following constraint:                -   The value of sps_video_parameter_set_id shall be the                    same in all SPSs that are referred to by coded                    pictures in a CVS.

    -   8) To solve the eighth problem, the syntax element        vps_general_hrd_params_present_flag is not signalled when        vps_general_hrd_params_present_flag is equal to 1, and when not        present, the value of vps_general_hrd_params_present_flag is        inferred to be equal to 0.        -   a. Alternatively, the value of            vps_general_hrd_params_present_flag is constrained to be            equal to 0 when each_layer_is_an_ols_flag is equal to 1.        -   b. Furthermore, the syntax condition for the syntax element            num_ols_hrd_params_minus1, i.e., “if(TotalNumOlss>1)”, is            removed, as it is not needed. This is because when            TotalNumOlss is equal to 1, the value of            each_layer_is_an_ols_flag would be equal to 1 and then the            value of vps_general_hrd_params_present_flag would equal to            0 then no HRD parameters would be signalled in the VPS at            all.            -   In some cases, when there is no ols_hrd_parameters( )                syntax structure is present in the VPS, the                general_hrd_parameters( ) syntax structure is not                signalled in the VPS.

    -   9) To solve the ninth problem, the HRD parameters for OLSs        containing only one layer are only signalled in SPSs, not in the        VPS.

6. Embodiments

Below are some example embodiments for aspects summarized above inSection 5, which can be applied to the VVC specification. The changedtexts are based on the latest VVC text in JVET-P2001-v14. Most relevantparts that have been added or modified are highlighted in underlineboldface, and some of the deleted parts are highlighted in italicsboldface. There are some other changes that are editorial in nature andthus not highlighted.

6.1. First Embodiment

6.1.1. VPS Syntax and Semantics

7.3.2.2 Video Parameter Set Syntax

Descriptor video_parameter_set rbsp( ) {  vps_video_parameter_set_idu(4)  vps_max_layers_minus1 u(6)  vps_max_sublayers_minus1 u(3)  if(vps_max_layers_minus1 > 0 && vps_max_sublayers_minus1 > 0 )  vps_all_layers_same_num_sublayers_flag u(1)  if(vps_max_layers_minus1 > 0 )   vps_all_independent_layers_flag u(1)  for(i = 0; i <= vps_max_layers_minus1; i++ ) {   vps_layer_id[ i ] u(6)  if( i > 0 && !vps_all_independent_layers_flag ) {   vps_independent_layer_flag[ i ] u(1)    if(!vps_independent_layer_flag[ i ] )     for( j = 0; j < i; j++ )     vps_direct_ref_layer_flag[ i ][ j ] u(1)   }  }  if(vps_max_layers_minus1 > 0 ) {   if( vps_all_independent_layers_flag )   each_layer_is_an_ols_flag u(1)   if( !each_layer_is_an_ols_flag ) {   if( !vps_all_independent_layers_flag )     ols_mode_idc u(2)    if(ols_mode_idc == 2 ) {     num_output_layer_sets_minus1 u(8)     for( i =1; i <= num_output_layer_sets_minus1; i ++)      for( j = 0; j <=vps_max_layers_minus1; j++ )       ols_output_layer_flag[ i ][ j ] u(1)   }   }  }  vps_num_ptls_ minus1 u(8)  for( i = 0; i <= vps_num_ptls_minus1 ; i++ ) {   if( i > 0)    pt_present_flag[ i ] u(1)   if(vps_max_sublayers_minus1 > 0 && !vps_all_layers_same_num_sublayers_flag)    ptl_max_temporal_id[ i ] u(3)  }  while( !byte_aligned( ) )  vps_ptl_byte_alignment_zero_bit /* equal to 0 */ u(1)  for( i = 0; i<= vps_num_ptls_ minus1 ; i++ )   profile_tier_level( pt_present_flag[ i], ptl_max_temporal_id[ i ] )  for( i = 0; i < TotalNumOlss; i++ )   if( vps_num_ptls_minus1  >   0 )    ols_ptl_idx[ i ] u(8)  if(!vps_all_independent_layers_flag) {   vps_num_dpb_params_ minus1 ue(v)  same_dpb_size_output_or_nonoutput_flag u(1)   if(vps_max_sublayers_minus1 > 0 )    vps_sublayer_dpb_params_present_flagu(1)  }  for( i = 0; i < VpsNumDpbParams ; i++ ) {   dpb_size_only_flag[i ] u(1)   if( vps_max_sublayers_minus1 > 0 &&!vps_all_layers_same_num_sublayers_flag )    dpb_max_temporal_id[ i ]u(3)   dpb_parameters( dpb_size_only_flag[ i ], dpb_max_temporal_id[ i],       vps_sublayer_dpb_params_present_flag )  }  for( i = 0; i <vps_max_layers_minus1 && VpsNumDpbParams > 1; i++ ) {   if(LayerUsedAsOutputLayerFlag [   i   ]   && !vps_independent_layer_flag[ i] )    layer_output_dpb_params_idx[ i ] ue(v)   if(LayerUsedAsRefLayerFlag[ i ] && !same_dpb_size_output_or_nonoutput_flag)    layer_nonoutput_dpb_params_idx[ i ] ue(v)  }   if(  !each_layer_is_an_ols_flag  )   vps_general_hrd_params_present_flag u(1) if( vps_general_hrd_params_present flag ) {   general_hrd_parameters( )  if( vps_max_sublayers_minus1 > 0)   vps_sublayer_cpb_params_present_flag u(1)   

  num_ols_hrd_params_minus1 ue(v)   for( i = 0; i <=num_ols_hrd_params_minus1; i++ ) {    if( vps_max_sublayers_minus1 > 0&& !vps_all_layers_same_num_sublayers_flag )     hrd_max_tid[ i ] u(3)   firstSubLayer = vps_sublayer_cpb_params_present_flag ? 0 :hrd_max_tid[ i ]    ols_hrd_parameters( firstSubLayer, hrd_max_tid[ i ])   }  if (   NumLayersInOls [   i   ]   >   1   &&num_ols_hrd_params_minus1 > 0 )  for( i = 1; i < TotalNumOlss; i++ )    ols_hrd_idx[ i ] ue(v)  }  vps_extension_flag u(1)  if(vps_extension_flag )   while( more_rbsp_data( ) )   vps_extension_data_flag u(1)  rbsp_trailing_bits( ) }7.4.3.2 Video Parameter Set RBSP Semanticsols_output_layer_flag[i][j] equal to 1 specifies that the layer withnuh_layer_id equal to vps_layer_id[j] is an output layer of the i-th OLSwhen ols_mode_idc is equal to 2. ols_output_layer_flag[i][j] equal to 0specifies that the layer with nuh_layer_id equal to vps_layer_id[j] isnot an output layer of the i-th OLS when ols_mode_idc is equal to 2.The variable NumOutputLayersInOls[i], specifying the number of outputlayers in the i-th OLS, and the variable OutputLayerIdInOls[i][j],specifying the nuh_layer_id value of the j-th output layer in the i-thOLS, are derived as follows:

NumOutputLayersInOls[ 0 ] = 1 (40) OutputLayerIdInOls[ 0 ][ 0 ] =vps_layer_id[ 0 ] LayerUsedAsOutputLayerFlag [   0   ]   =   1 for(   i  =   1,   i   <=   vps_max_layers_minus1;  i++   )   {   if(  each_layer_is_an_ols_flag  ||   ols_mode_idc  <   2   )   LayerUsedAsOutputLayerFlag [   i   ]   =   1   if( ols_mode_idc  ==   2)    LayerUsedAsOutputLayerFlag [   i   ]   =   0 } for( i = 1; i <TotalNumOlss; i++ ) {  if( each_layer_is_an_ols_flag || ols_mode_idc ==0 ) {   NumOutputLayersInOls[ i ] = 1   OutputLayerIdInOls[ i ][ 0 ] =vps_layer_id[ i ]  } else if( ols_mode_idc == 1 ) {  NumOutputLayersInOls[ i ] = i + 1   for( j = 0; j <NumOutputLayersInOls[ i ]; j++ )    OutputLayerIdInOls[ i ][ j ] =vps_layer_id[ j ]  } else if( ols_mode_idc == 2 ) {   for( j = 0; j <=vps_max_layers_minus1; j++ )    layerIncludedInOlsFlag[ i ][ j ] = 0  for( k = 0, j = 0; k <= vps_max_layers_minus1; k++ )    if(ols_output_layer_flag[ i ][ k ] ) {     layerIncludedInOlsFlag[ i ][ k ]= 1      LayerUsedAsOutputLayerFlag [   k   ]   =   1    OutputLayerIdx[ i ][ j ] = k     OutputLayerIdInOls[ i ][ j++ ] =vps layer id[ k ]    }   NumOutputLayersInOls[ i ] = j   for( j = 0; j <NumOutputLayersInOls[ i ]; j++ ) {    idx = OutputLayerIdx[ i ][ j ]   for( k = 0; k < NumRefLayers[ idx ]; k++ )    layerIncludedInOlsFlag[ i ][ RefLayerIdx[ idx ][ k ] ] = 1   }  } }For each value of i in the range of 0 to vps_max_layers_minus1,inclusive, the values of LayerUsedAsRefLayerFlag[i] andLayerUsedAsOutputLayerFlag[i] shall not be both equal to 0. In otherwords, there shall be no layer that is neither a direct reference layerof any other layer nor an output layer of at least one OLS.For each OLS, there shall be at least one layer that is an output layer.In other words, for any value of i in the range of 0 to TotalNumOlss−1,inclusive, the value of NumOutputLayersInOls[i] shall be greater than orequal to 1.The variable NumLayersInOls[i], specifying the number of layers in thei-th OLS, and the variable LayerIdInOls[i][j], specifying thenuh_layer_id value of the j-th layer in the i-th OLS, are derived asfollows:

NumLayersInOls[ 0 ] = 1 (41) LayerIdInOls[ 0 ][ 0 ] = vps_layer_id[ 0 ]for( i = 1; i < TotalNumOlss; i++ ) {  if( each_layer_is_an_ols_flag ) {  NumLayersInOls[ i ] = 1   LayerIdInOls[ i ][ 0 ] = vps_layer_id[ i ] } else if( ols_mode_idc == 0 || ols_mode_idc == 1 ) {   NumLayersInOls[i ] = i + 1   for( j = 0; j < NumLayersInOls[ i ]; j++ )   LayerIdInOls[ i ][ j ] = vps_layer_id[ j ]  } else if( ols_mode_idc== 2 ) {   for( k = 0, j = 0; k <= vps_max_layers_minus1; k++ )    if(layerIncludedInOlsFlag[ i ][ k ] )     LayerIdInOls[ i ][ j++ ] =vps_layer_id[ k ]   NumLayersInOls[ i ] = j  } }

-   -   NOTE—The 0-th OLS contains only the lowest layer (i.e., the        layer with nuh_layer_id equal to vps_layer_id[0]) and for the        0-th OLS the only included layer is output.        The variable OlsLayerIdx[i][j], specifying the OLS layer index        of the layer with nuh_layer_id equal to LayerIdInOls[i][j], is        derived as follows:

for( i = 0; i < TotalNumOlss; i++ ) (42)  for j = 0; j < NumLayersInOls[i ]; j++ )   OlsLayeIdx[ i ][ LayerIdInOls[ i ][ j ] ] = jThe lowest layer in each OLS shall be an independent layer. In otherwords, for each i in the range of 0 to TotalNumOlss−1, inclusive, thevalue of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]]shall be equal to 1.Each layer shall be included in at least one OLS specified by the VPS.In other words, for each layer with a particular value of nuh_layer_idnuhLayerId equal to one of vps_layer_id[k] for k in the range of 0 tovps_max_layers_minus1, inclusive, there shall be at least one pair ofvalues of i and j, where i is in the range of 0 to TotalNumOlss−1,inclusive, and j is in the range of NumLayersInOls[i]−1, inclusive, suchthat the value of LayerIdInOls[i][j] is equal to nuhLayerId.vps_num_ptls_minus1 plus 1 specifies the number of profile_tier_level( )syntax structures in the VPS.pt_present_flag[i] equal to 1 specifies that profile, tier, and generalconstraints information are present in the i-th profile_tier_level( )syntax structure in the VPS. pt_present_flag[i] equal to 0 specifiesthat profile, tier, and general constraints information are not presentin the i-th profile_tier_level( ) syntax structure in the VPS. The valueof pt_present_flag[0] is inferred to be equal to 1. Whenpt_present_flag[i] is equal to 0, the profile, tier, and generalconstraints information for the i-th profile_tier_level( ) syntaxstructure in the VPS are inferred to be the same as that for the(i−1)-th profile_tier_level( ) syntax structure in the VPS.ptl_max_temporal_id[i] specifies the TemporalId of the highest sublayerrepresentation for which the level information is present in the i-thprofile_tier_level( ) syntax structure in the VPS. The value ofptl_max_temporal_id[i] shall be in the range of 0 tovps_max_sublayers_minus1, inclusive. When vps_max_sublayers_minus1 isequal to 0, the value of ptl_max_temporal_id[i] is inferred to be equalto 0. When vps_max_sublayers_minus1 is greater than 0 andvps_all_layers_same_num_sublayers_flag is equal to 1, the value ofptl_max_temporal_id[i] is inferred to be equal tovps_max_sublayers_minus1.vps_ptl_byte_alignment_zero_bit shall be equal to 0.ols_ptl_idx[i] specifies the index, to the list of profile_tier_level( )syntax structures in the VPS, of the profile_tier_level( ) syntaxstructure that applies to the i-th OLS. When present, the value ofols_ptl_idx[i] shall be in the range of 0 to vps_num_ptls_minus1,inclusive. When vps_num_ptls_minus1 is equal to 0, the value ofols_ptl_idx[i] is inferred to be equal to 0.When NumLayersInOls[i] is equal to 1, the profile_tier_level( ) syntaxstructure that applies to the i-th OLS is also present in the SPSreferred to by the layer in the i-th OLS.vps_num_dpb_params_minus1 plus 1 specifies the number of dpb_parameters() syntax structures in the VPS. When present, the value ofvps_num_dpb_params_minus1 shall be in the range of 0 to 15, inclusive.The variable VpsNumDpbParams is derived as follows:

if(   !vps_all_independent_layers_flag  ) (42)   VpsNumDpbParams   =  vps_num_dpb_params_minus1  +   1 else   VpsNumDpbParams   =   0same_dpb_size_output_or_nonoutput_flag equal to 1 specifies that thereis no layer_nonoutput_dpb_params_idx[i] syntax element present in theVPS. same_dpb_size_output_or_nonoutput_flag equal to 0 specifies thatthere may or may not be layer_nonoutput_dpb_params_idx[i] syntaxelements present in the VPS. When not present, the value ofsame_dpb_size_output_or_nonoutput_flag is inferred to be equal to 1.vps_sublayer_dpb_params_present_flag is used to control the presence ofmax_dec_pic_buffering_minus1[ ], max_num_reorder_pics[ ], andmax_latency_increase_plus1[ ] syntax elements in the dpb_parameters( )syntax structures in the VPS. When not present,vps_sub_dpb_params_info_present_flag is inferred to be equal to 0.dpb_size_only_flag[i] equal to 1 specifies that themax_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntaxelements are not present in the i-th dpb_parameters( ) syntax structuresthe VPS. dpb_size_only_flag[i] equal to 0 specifies that themax_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntaxelements may be present in the i-th dpb_parameters( ) syntax structuresthe VPS.dpb_max_temporal_id[i] specifies the TemporalId of the highest sublayerrepresentation for which the DPB parameters may be present in the i-thdpb_parameters( ) syntax structure in the VPS. The value ofdpb_max_temporal_id[i] shall be in the range of 0 tovps_max_sublayers_minus1, inclusive. When vps_max_sublayers_minus1 isequal to 0, the value of dpb_max_temporal_id[i] is inferred to be equalto 0. When vps_max_sublayers_minus1 is greater than 0 andvps_all_layers_same_num_sublayers_flag is equal to 1, the value ofdpb_max_temporal_id[i] is inferred to be equal tovps_max_sublayers_minus1.layer_output_dpb_params_idx[i] specifies the index, to the list ofdpb_parameters( ) syntax structures in the VPS, of the dpb_parameters( )syntax structure that applies to the i-th layer when it is an outputlayer in an OLS. When present, the value oflayer_output_dpb_params_idx[i] shall be in the range of 0 toVpsNumDpbParams−1, inclusive.If vps_independent_layer_flag[i] is equal to 1, the dpb_parameters( )syntax structure that applies to the i-th layer when it is an outputlayer is the dpb_parameters( ) syntax structure present in the SPSreferred to by the layer.Otherwise (vps_independent_layer_flag[i] is equal to 0), the followingapplies:

-   -   When VpsNumDpbParams is equal to 1, the value of        layer_output_dpb_params_idx[i] is inferred to be equal to 0.    -   It is a requirement of bitstream conformance that the value of        layer_output_dpb_params_idx[i] shall be such that        dpb_size_only_flag[layer_output_dpb_params_idx[i]] is equal to        0.        layer_nonoutput_dpb_params_idx[i] specifies the index, to the        list of dpb_parameters( ) syntax structures in the VPS, of the        dpb_parameters( ) syntax structure that applies to the i-th        layer when it is a non-output layer in an OLS. When present, the        value of layer_nonoutput_dpb_params_idx[i] shall be in the range        of 0 to VpsNumDpbParams−1, inclusive.        If same_dpb_size_output_or_nonoutput_flag is equal to 1, the        following applies:    -   If vps_independent_layer_flag[i] is equal to 1, the        dpb_parameters( ) syntax structure that applies to the i-th        layer when it is a non-output layer is the dpb_parameters( )        syntax structure present in the SPS referred to by the layer.    -   Otherwise (vps_independent_layer_flag[i] is equal to 0), the        value of layer_nonoutput_dpb_params_idx[i] is inferred to be        equal to layer_output_dpb_params_idx[i].        Otherwise (same_dpb_size_output_or_nonoutput_flag is equal to        0), when VpsNumDpbParams is equal to 1, the value of        layer_output_dpb_params_idx[i] is inferred to be equal to 0.        vps_general_hrd_params_present_flag equal to 1 specifies that        the syntax structure general_hrd_parameters( ) and other HRD        parameters are present in the VPS RBSP syntax structure.        vps_general_hrd_params_present_flag equal to 0 specifies that        the syntax structure general_hrd_parameters( ) and other HRD        parameters are not present in the VPS RBSP syntax structure.        When not present, the value of        vps_general_hrd_params_present_flag is inferred to be equal to        0.        vps_sublayer_cpb_params_present_flag equal to 1 specifies that        the i-th ols_hrd_parameters( ) syntax structure in the VPS        contains HRD parameters for the sublayer representations with        TemporalId in the range of 0 to hrd_max_tid[i], inclusive.        vps_sublayer_cpb_params_present_flag equal to 0 specifies that        the i-th ols_hrd_parameters( ) syntax structure in the VPS        contains HRD parameters for the sublayer representation with        TemporalId equal to hrd_max_tid[i] only. When        vps_max_sublayers_minus1 is equal to 0, the value of        vps_sublayer_cpb_params_present_flag is inferred to be equal to        0.        When vps_sublayer_cpb_params_present_flag is equal to 0, the HRD        parameters for the sublayer representations with TemporalId in        the range of 0 to hrd_max_tid[i]−1, inclusive, are inferred to        be the same as that for the sublayer representation with        TemporalId equal to hrd_max_tid[i]. These include the HRD        parameters starting from the fixed_pic_rate_general_flag[i]        syntax element till the sublayer_hrd_parameters(i) syntax        structure immediately under the condition        “if(general_vcl_hrd_params_present_flag)” in the        ols_hrd_parameters syntax structure.        num_ols_hrd_params_minus1 plus 1 specifies the number of        ols_hrd_parameters( ) syntax structures present in the        general_hrd_parameters( ) syntax structure when        vps_general_hrd_params_present_flag is equal to 1. The value of        num_ols_hrd_params_minus1 shall be in the range of 0 to 63,        inclusive. When TotalNumOlss is equal to 1, the value of        num_ols_hrd_params_minus1 is inferred to be equal to 0.        hrd_max_tid[i] specifies the TemporalId of the highest sublayer        representation for which the HRD parameters are contained in the        i-th ols_hrd_parameters( ) syntax structure. The value of        hrd_max_tid[i] shall be in the range of 0 to        vps_max_sublayers_minus1, inclusive. When        vps_max_sublayers_minus1 is equal to 0, the value of        hrd_max_tid[i] is inferred to be equal to 0. When        vps_max_sublayers_minus1 is greater than 0 and        vps_all_layers_same_num_sublayers_flag is equal to 1, the value        of hrd_max_tid[i] is inferred to be equal to        vps_max_sublayers_minus1.        ols_hrd_idx[i] specifies the index, to the list of        ols_hrd_parameters( ) syntax structures in the VPS, of the        ols_hrd_parameters( ) syntax structure that applies to the i-th        OLS when NumLayersInOls[i] is greater than 1. When present, the        value of ols_hrd_idx[[i] shall be in the range of 0 to        num_ols_hrd_params_minus1, inclusive. When NumLayersInOls[i] is        greater than 1 and num_ols_hrd_params_minus1 is equal to 0, the        value of ols_hrd_idx[[i] is inferred to be equal to 0.        vps_extension_flag equal to 0 specifies that no        vps_extension_data_flag syntax elements are present in the VPS        RBSP syntax structure. vps_extension_flag equal to 1 specifies        that there are vps_extension_data_flag syntax elements present        in the VPS RBSP syntax structure.        vps_extension_data_flag may have any value. Its presence and        value do not affect decoder conformance to profiles specified in        this version of this Specification. Decoders conforming to this        version of this Specification shall ignore all        vps_extension_data_flag syntax elements.        6.1.2. SPS Semantics        7.4.3.3 Sequence Parameter Set RB SP Semantics        An SPS RB SP shall be available to the decoding process prior to        it being referenced, included in at least one AU with TemporalId        equal to 0 or provided through external means.        All SPS NAL units with a particular value of        sps_seq_parameter_set_id in a CVS shall have the same content.        sps_decoding_parameter_set_id, when greater than 0, specifies        the value of dps_decoding_parameter_set_id for the DPS referred        to by the SPS. When sps_decoding_parameter_set_id is equal to 0,        the SPS does not refer to a DPS and no DPS is referred to when        decoding each CLVS referring to the SPS. The value of        sps_decoding_parameter_set_id shall be the same in all SPSs that        are referred to by coded pictures in a bitstream.        sps_video_parameter_set_id, when greater than 0, specifies the        value of vps_video_parameter_set_id for the VPS referred to by        the SPS. The value of sps_video_parameter_set_id shall be the        same in all SPSs that are referred to by coded pictures in a CVS        and that have sps_video_parameter_set_id greater than 0.        When sps_video_parameter_set_id is equal to 0, the following        applies:    -   The SPS does not refer to a VPS.    -   No VPS is referred to when decoding each CLVS referring to the        SPS.    -   The value of vps_max_layers_minus1 is inferred to be equal to 0.    -   The CVS shall contain only one layer (i.e., all VCL NAL unit in        the CVS shall have the same value of nuh_layer_id).    -   The value of GeneralLayerIdx[nuh_layer_id] is inferred to be        equal to 0.    -   The value of        vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is        inferred to be equal to 1.        When vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]        is equal to 1, the SPS referred to by a CLVS with a particular        nuh_layer_id value nuhLayerId shall have nuh_layer_id equal to        nuhLayerId.        6.1.3. Slice Header Semantics        7.4.8.1 General Slice Header Semantics        . . .        slice_type specifies the coding type of the slice according to        Table 9.

TABLE 9 Name association to slice_type slice_type Name of slice_type 0 B(B slice) 1 P (P slice) 2 I (I slice)When nal_unit_type is in the range of IDR_W_RADL to CRA_NUT, inclusive,and vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equalto 1, slice_type shall be equal to 2.

FIG. 1 is a block diagram showing an example video processing system1900 in which various techniques disclosed herein may be implemented.Various implementations may include some or all of the components of thesystem 1900. The system 1900 may include input 1902 for receiving videocontent. The video content may be received in a raw or uncompressedformat, e.g, 8 or 10 bit multi-component pixel values, or may be in acompressed or encoded format. The input 1902 may represent a networkinterface, a peripheral bus interface, or a storage interface. Examplesof network interface include wired interfaces such as Ethernet, passiveoptical network (PON), etc. and wireless interfaces such as Wi-Fi orcellular interfaces.

The system 1900 may include a coding component 1904 that may implementthe various coding or encoding methods described in the presentdocument. The coding component 1904 may reduce the average bitrate ofvideo from the input 1902 to the output of the coding component 1904 toproduce a coded representation of the video. The coding techniques aretherefore sometimes called video compression or video transcodingtechniques. The output of the coding component 1904 may be eitherstored, or transmitted via a communication connected, as represented bythe component 1906. The stored or communicated bitstream (or coded)representation of the video received at the input 1902 may be used bythe component 1908 for generating pixel values or displayable video thatis sent to a display interface 1910. The process of generatinguser-viewable video from the bitstream is sometimes called videodecompression. Furthermore, while certain video processing operationsare referred to as “coding” operations or tools, it will be appreciatedthat the coding tools or operations are used at an encoder andcorresponding decoding tools or operations that reverse the results ofthe coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include SATA (serial advanced technology attachment), PCI,IDE interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

FIG. 2 is a block diagram of a video processing apparatus 3600. Theapparatus 3600 may be used to implement one or more of the methodsdescribed herein. The apparatus 3600 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 3600 may include one or more processors 3602, one or morememories 3604 and video processing hardware 3606. The processor(s) 3602may be configured to implement one or more methods described in thepresent document. The memory (memories) 3604 may be used for storingdata and code used for implementing the methods and techniques describedherein. The video processing hardware 3606 may be used to implement, inhardware circuitry, some techniques described in the present document.In some embodiments, the hardware 3606 may be partially or fully locatedwithin the processor(s) 3602, e.g., a graphics processor.

FIG. 4 is a block diagram that illustrates an example video codingsystem 100 that may utilize the techniques of this disclosure.

As shown in FIG. 4 , video coding system 100 may include a source device110 and a destination device 120. Source device 110 generates encodedvideo data which may be referred to as a video encoding device.Destination device 120 may decode the encoded video data generated bysource device 110 which may be referred to as a video decoding device.

Source device 110 may include a video source 112, a video encoder 114,and an input/output (I/O) interface 116.

Video source 112 may include a source such as a video capture device, aninterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources. The video data may comprise one or more pictures. Videoencoder 114 encodes the video data from video source 112 to generate abitstream. The bitstream may include a sequence of bits that form acoded representation of the video data. The bitstream may include codedpictures and associated data. The coded picture is a codedrepresentation of a picture. The associated data may include sequenceparameter sets, picture parameter sets, and other syntax structures. I/Ointerface 116 may include a modulator/demodulator (modem) and/or atransmitter. The encoded video data may be transmitted directly todestination device 120 via I/O interface 116 through network 130 a. Theencoded video data may also be stored onto a storage medium/server 130 bfor access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface126 may acquire encoded video data from the source device 110 or thestorage medium/server 130 b. Video decoder 124 may decode the encodedvideo data. Display device 122 may display the decoded video data to auser. Display device 122 may be integrated with the destination device120, or may be external to destination device 120 which be configured tointerface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a videocompression standard, such as the High Efficiency Video Coding (HEVC)standard, Versatile Video Coding (VVM) standard and other current and/orfurther standards.

FIG. 5 is a block diagram illustrating an example of video encoder 200,which may be video encoder 114 in the system 100 illustrated in FIG. 4 .

Video encoder 200 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 5 , video encoder200 includes a plurality of functional components. The techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 200. In some examples, a processor may be configured toperform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partitionunit 201, a predication unit 202 which may include a mode select unit203, a motion estimation unit 204, a motion compensation unit 205 and anintra prediction unit 206, a residual generation unit 207, a transformunit 208, a quantization unit 209, an inverse quantization unit 210, aninverse transform unit 211, a reconstruction unit 212, a buffer 213, andan entropy encoding unit 214.

In other examples, video encoder 200 may include more, fewer, ordifferent functional components. In an example, predication unit 202 mayinclude an intra block copy (IBC) unit. The IBC unit may performpredication in an IBC mode in which at least one reference picture is apicture where the current video block is located.

Furthermore, some components, such as motion estimation unit 204 andmotion compensation unit 205 may be highly integrated, but arerepresented in the example of FIG. 5 separately for purposes ofexplanation.

Partition unit 201 may partition a picture into one or more videoblocks. Video encoder 200 and video decoder 300 may support variousvideo block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter,e.g., based on error results, and provide the resulting intra- orinter-coded block to a residual generation unit 207 to generate residualblock data and to a reconstruction unit 212 to reconstruct the encodedblock for use as a reference picture. In some example, Mode select unit203 may select a combination of intra and inter predication (CIIP) modein which the predication is based on an inter predication signal and anintra predication signal. Mode select unit 203 may also select aresolution for a motion vector (e.g., a sub-pixel or integer pixelprecision) for the block in the case of inter-predication.

To perform inter prediction on a current video block, motion estimationunit 204 may generate motion information for the current video block bycomparing one or more reference frames from buffer 213 to the currentvideo block. Motion compensation unit 205 may determine a predictedvideo block for the current video block based on the motion informationand decoded samples of pictures from buffer 213 other than the pictureassociated with the current video block.

Motion estimation unit 204 and motion compensation unit 205 may performdifferent operations for a current video block, for example, dependingon whether the current video block is in an I slice, a P slice, or a Bslice.

In some examples, motion estimation unit 204 may perform uni-directionalprediction for the current video block, and motion estimation unit 204may search reference pictures of list 0 or list 1 for a reference videoblock for the current video block. Motion estimation unit 204 may thengenerate a reference index that indicates the reference picture in list0 or list 1 that contains the reference video block and a motion vectorthat indicates a spatial displacement between the current video blockand the reference video block. Motion estimation unit 204 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the current video block. Motioncompensation unit 205 may generate the predicted video block of thecurrent block based on the reference video block indicated by the motioninformation of the current video block.

In other examples, motion estimation unit 204 may perform bi-directionalprediction for the current video block, motion estimation unit 204 maysearch the reference pictures in list 0 for a reference video block forthe current video block and may also search the reference pictures inlist 1 for another reference video block for the current video block.Motion estimation unit 204 may then generate reference indexes thatindicate the reference pictures in list 0 and list 1 containing thereference video blocks and motion vectors that indicate spatialdisplacements between the reference video blocks and the current videoblock. Motion estimation unit 204 may output the reference indexes andthe motion vectors of the current video block as the motion informationof the current video block. Motion compensation unit 205 may generatethe predicted video block of the current video block based on thereference video blocks indicated by the motion information of thecurrent video block.

In some examples, motion estimation unit 204 may output a full set ofmotion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may do not output a fullset of motion information for the current video. Rather, motionestimation unit 204 may signal the motion information of the currentvideo block with reference to the motion information of another videoblock. For example, motion estimation unit 204 may determine that themotion information of the current video block is sufficiently similar tothe motion information of a neighboring video block.

In one example, motion estimation unit 204 may indicate, in a syntaxstructure associated with the current video block, a value thatindicates to the video decoder 300 that the current video block has thesame motion information as the another video block.

In another example, motion estimation unit 204 may identify, in a syntaxstructure associated with the current video block, another video blockand a motion vector difference (MVD). The motion vector differenceindicates a difference between the motion vector of the current videoblock and the motion vector of the indicated video block. The videodecoder 300 may use the motion vector of the indicated video block andthe motion vector difference to determine the motion vector of thecurrent video block.

As discussed above, video encoder 200 may predictively signal the motionvector. Two examples of predictive signaling techniques that may beimplemented by video encoder 200 include advanced motion vectorpredication (AMVP) and merge mode signaling.

Intra prediction unit 206 may perform intra prediction on the currentvideo block. When intra prediction unit 206 performs intra prediction onthe current video block, intra prediction unit 206 may generateprediction data for the current video block based on decoded samples ofother video blocks in the same picture. The prediction data for thecurrent video block may include a predicted video block and varioussyntax elements.

Residual generation unit 207 may generate residual data for the currentvideo block by subtracting (e.g., indicated by the minus sign) thepredicted video block(s) of the current video block from the currentvideo block. The residual data of the current video block may includeresidual video blocks that correspond to different sample components ofthe samples in the current video block.

In other examples, there may be no residual data for the current videoblock for the current video block, for example in a skip mode, andresidual generation unit 207 may not perform the subtracting operation.

Transform processing unit 208 may generate one or more transformcoefficient video blocks for the current video block by applying one ormore transforms to a residual video block associated with the currentvideo block.

After transform processing unit 208 generates a transform coefficientvideo block associated with the current video block, quantization unit209 may quantize the transform coefficient video block associated withthe current video block based on one or more quantization parameter (QP)values associated with the current video block.

Inverse quantization unit 210 and inverse transform unit 211 may applyinverse quantization and inverse transforms to the transform coefficientvideo block, respectively, to reconstruct a residual video block fromthe transform coefficient video block. Reconstruction unit 212 may addthe reconstructed residual video block to corresponding samples from oneor more predicted video blocks generated by the predication unit 202 toproduce a reconstructed video block associated with the current blockfor storage in the buffer 213.

After reconstruction unit 212 reconstructs the video block, loopfiltering operation may be performed reduce video blocking artifacts inthe video block.

Entropy encoding unit 214 may receive data from other functionalcomponents of the video encoder 200. When entropy encoding unit 214receives the data, entropy encoding unit 214 may perform one or moreentropy encoding operations to generate entropy encoded data and outputa bitstream that includes the entropy encoded data.

FIG. 6 is a block diagram illustrating an example of video decoder 300which may be video decoder 114 in the system 100 illustrated in FIG. 4 .

The video decoder 300 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 5 , the videodecoder 300 includes a plurality of functional components. Thetechniques described in this disclosure may be shared among the variouscomponents of the video decoder 300. In some examples, a processor maybe configured to perform any or all of the techniques described in thisdisclosure.

In the example of FIG. 6 , video decoder 300 includes an entropydecoding unit 301, a motion compensation unit 302, an intra predictionunit 303, an inverse quantization unit 304, an inverse transformationunit 305, and a reconstruction unit 306 and a buffer 307. Video decoder300 may, in some examples, perform a decoding pass generally reciprocalto the encoding pass described with respect to video encoder 200 (FIG. 5).

Entropy decoding unit 301 may retrieve an encoded bitstream. The encodedbitstream may include entropy coded video data (e.g., encoded blocks ofvideo data). Entropy decoding unit 301 may decode the entropy codedvideo data, and from the entropy decoded video data, motion compensationunit 302 may determine motion information including motion vectors,motion vector precision, reference picture list indexes, and othermotion information. Motion compensation unit 302 may, for example,determine such information by performing the AMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used with sub-pixelprecision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used byvideo encoder 20 during encoding of the video block to calculateinterpolated values for sub-integer pixels of a reference block. Motioncompensation unit 302 may determine the interpolation filters used byvideo encoder 200 according to received syntax information and use theinterpolation filters to produce predictive blocks.

Motion compensation unit 302 may uses some of the syntax information todetermine sizes of blocks used to encode frame(s) and/or slice(s) of theencoded video sequence, partition information that describes how eachmacroblock of a picture of the encoded video sequence is partitioned,modes indicating how each partition is encoded, one or more referenceframes (and reference frame lists) for each inter-encoded block, andother information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for examplereceived in the bitstream to form a prediction block from spatiallyadjacent blocks. Inverse quantization unit 303 inverse quantizes, i.e.,de-quantizes, the quantized video block coefficients provided in thebitstream and decoded by entropy decoding unit 301. Inverse transformunit 303 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with thecorresponding prediction blocks generated by motion compensation unit202 or intra-prediction unit 303 to form decoded blocks. If desired, adeblocking filter may also be applied to filter the decoded blocks inorder to remove blockiness artifacts. The decoded video blocks are thenstored in buffer 307, which provides reference blocks for subsequentmotion compensation/intra predication and also produces decoded videofor presentation on a display device.

A listing of solutions preferred by some embodiments is provided next.

The following solutions show example embodiments of techniques discussedin the previous section (e.g., item 1).

1. A method of video processing (e.g., method 600 in FIG. 3 ),comprising: performing a conversion between a video comprising one ormore scalable video layers and a coded representation of the video,wherein the coded representation conforms to a format rule, wherein theformat rule specifies that a value of a field indicative of a slice typeof a slice is set to indicate a type of intra slice in case that acorresponding network abstraction layer unit type is in a predeterminedrange and that a corresponding video layer flag indicates that a videolayer corresponding to the slice does not use inter-layer prediction.

2. The method of solution 1, wherein the slice type of the slice is setto 2.

3. The method of solution 1, wherein the pre-determined range is fromIDR_W_RADL to CRA_NUT, both inclusive.

4. A method of video processing, comprising: performing a conversionbetween a video comprising one or more scalable video layers and a codedrepresentation of the video, wherein the coded representation conformsto a format rule, wherein the format rule specifies that an indicationfor an index to a syntax structure describing a profile and tier levelof the one or more scalable video layers is inferred to be equal to 0 incase the index is excluded from the coded representation.

5. The method of solution 4, wherein the indication comprises anols_ptl_idx[i] syntax element, where i is an integer.

6. A method of video processing, comprising: performing a conversionbetween a video comprising one or more scalable video layers and a codedrepresentation of the video, wherein the coded representation contains aplurality of output layer sets (OLSs), wherein each OLS is a set oflayers in the coded representation with the set of layers specified tobe output, wherein the coded representation conforms to a format rule,wherein the format rule specifies that a video parameter set of thecoded representation is permitted to have repetitive informationregarding a profile, a tier and a level of an OLS in case that the OLScomprises a single layer.

7. The method of solution 6, wherein the format rule specifies to signala number field indicative of a total number of the set of informationregarding a profile, a tier and a level for the plurality of OLSs, wherethe total number is at least one.

8. The method of any of solutions 1-7, wherein the performing theconversion comprising encoding the video to generate the codedrepresentation.

9. The method of any of solutions 1-7, wherein the performing theconversion comprises parsing and decoding the coded representation togenerate the video.

10. A video decoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions 1 to 9.

11. A video encoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions 1 to 9.

12. A computer program product having computer code stored thereon, thecode, when executed by a processor, causes the processor to implement amethod recited in any of solutions 1 to 9.

13. A method, apparatus or system described in the present document.

With respect to FIGS. 7A to 7I, the following listed solutions may bepreferably implemented in some embodiments.

For example, the following solutions may be implemented according toitem 1 in previous section.

1. A method of video processing (e.g., method 710 depicted in FIG. 7A),comprising performing (712) a conversion between a video comprising oneor more scalable video layers and a bitstream of the video, wherein thevideo comprises one or more video pictures comprising one or moreslices; wherein the bitstream conforms to a format rule, wherein theformat rule specifies that a value of a field indicative of a slice typeof a slice is set to indicate a type of intra slice in case that acorresponding network abstraction layer unit type is in a predeterminedrange and that a corresponding video layer flag indicates that a videolayer corresponding to the slice does not use inter-layer prediction.

2. The method of solution 1, wherein the slice type of the slice is setto 2.

3. The method of solution 1, wherein the pre-determined range is fromIDR_W_RADL to CRA_NUT, both inclusive, wherein IDR_W_RADL indicates aslice having an instantaneous decoding refresh type and wherein CRA_NUTindicates a slice having a clean random access type.

4. The method of any of solutions 1-3, wherein the corresponding videolayer flag corresponds tovps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]], whereinnuh_layer_id corresponds to an identifier of the video layer,GeneralLayerIdx[ ] is an index of the video layer andvps_independent_layer_flag corresponds to the video layer flag.

5. The method of any of solutions 1-4, wherein the performing theconversion comprising encoding the video into the bitstream.

6. The method of any of solutions 1-4, wherein the performing theconversion comprises parsing and decoding the video from the bitstream.

7. A method for storing bitstream of a video, comprising: generating abitstream from the video comprising one or more scalable video layers;and storing the bitstream in a non-transitory computer-readablerecording medium; wherein the video comprises one or more video picturescomprising one or more slices; wherein the bitstream conforms to aformat rule, wherein the format rule specifies that a value of a fieldindicative of a slice type of a slice is set to indicate a type of Islice in case that a corresponding network abstraction layer unit typeis in a predetermined range and that a corresponding video layer flagindicates that a video layer corresponding to the slice does not useinter-layer prediction.

For example, the following solutions may be implemented according toitem 5 in previous section.

1. A method of video processing (e.g., method 720 depicted in FIG. 7B),comprising performing (722) a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), eachcomprising one or more of the plurality of scalable video layers, andthe bitstream conforms to a format rule, wherein the format rulespecifies that, for an OLS having a single layer, a profile-tier-level(PTL) syntax structure that indicates a profile, a tier and a level forthe OLS is included in a video parameter set for the bitstream, and thePTL syntax structure for the OLS is also included in a sequenceparameter set coded in the bitstream.

2. The method of solution 1, wherein the format rule specifies that asyntax element is included in the video parameter set indicative of anumber of PTL syntax structures coded in the video parameter set.

3. The method of solution 2, wherein the number of PTL syntax structurescoded in the video parameter set is equal to a value of the syntaxelement plus one.

4. The method of solution 2, wherein the number of PTL syntax structurescoded in the video parameter set is equal to a value of the syntaxelement.

5. The method of solution 4, wherein the format rule specifies that thesyntax element is coded in the video parameter set, during encoding, orparsed from the video parameter set, during decoding, when it isdetermined that one or more of the plurality of OLSs contain more thanone video layer.

6. The method of solution 4, wherein the format rule specifies that thesyntax element is coded in the video parameter set, during encoding, orparsed from the video parameter set, during decoding, when it isdetermined that a number of video layers is greater than 0 and one ormore of the video layers uses inter-layer prediction.

7. The method of any of solutions 1 to 6, wherein the format rulefurther specified that, for an OLS having a single layer, a decodedpicture buffer size parameter for the OLS is included in a videoparameter set for the bitstream, and the decoded picture buffer sizeparameter for the OLS is also included in a sequence parameter set codedin the bitstream.

8. The method of any of solutions 1 to 6, wherein the format rulefurther specified that, for an OLS having a single layer, parameterinformation of the decoded picture buffer for the OLS is included in avideo parameter set for the bitstream, and the parameter information ofthe decoded picture buffer for the OLS is also included in a sequenceparameter set coded in the bitstream.

For example, the following solutions may be implemented according toitem 6 in previous section.

9. A method of video processing (e.g., method 730 depicted in FIG. 7C),comprising: performing (732) a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifies arelationship between occurrence of a number of profile-tier-level (PTL)syntax structures in a video parameter set for the bitstream and a bytealignment syntax field in the video parameter set; wherein each PTLsyntax structure indicates a profile, a tier and a level of one or moreof the plurality of OLSs.

10. The method of solution 9, wherein the format rule specifies that, atleast one PTL syntax structure is included in the video parameter set,and due to inclusion of the at least one PTL syntax structure, one ormore instances of the byte alignment syntax field are included in thevideo parameter set.

11. The method of solution 10, wherein the byte alignment syntax fieldis one bit.

12. The method of solution 11, wherein the value of each of the one ormore instances of byte alignment syntax field has a value 0.

For example, the following solutions may be implemented according toitem 2 in previous section.

13. A method of video processing (e.g., method 740 depicted in FIG. 7D),comprising performing (742) a conversion between a video comprising aplurality of scalable video layers and a bitstream of the video, whereinthe bitstream comprises a plurality of output layer sets (OLSs), eachcomprising one or more of the plurality of scalable video layers, andthe bitstream conforms to a format rule, wherein the format rulespecifies that: during encoding, a syntax element indicative of an indexto a syntax structure describing a profile, a tier and a level of one ormore of the plurality of OLSs is excluded from a video parameter set forthe bitstream in case that a value of the index is zero, or, duringdecoding, the value is inferred to be zero in case that the syntaxelement is not present in the bitstream.

14. The method of solution 13, wherein the index is to a syntaxstructure that indicates a profile, a tier and a level of at least oneof the OLSs.

15. A method for storing bitstream of a video, comprising: generating abitstream from the video comprising a plurality of video layers, andstoring the bitstream in a non-transitory computer-readable recordingmedium; wherein the bitstream comprises a plurality of output layer sets(OLSs), each comprising one or more of the plurality of video layers,and the bitstream conforms to a format rule, wherein the format rulespecifies that, for an OLS having a single layer, a profile-tier-level(PTL) syntax structure that indicates a profile, a tier and a level forthe OLS is included in a video parameter set for the bitstream, and thePTL syntax structure for the OLS is also included in a sequenceparameter set coded in the bitstream.

16. The method of any of solutions 1-14, wherein the performing theconversion comprises encoding the video into the bitstream; and themethod further comprises storing the bitstream in a non-transitorycomputer-readable recording medium.

For example, the following solutions may be implemented according toitem 3 in previous section.

1. A method of video processing (e.g., method 750 depicted in FIG. 7E),comprising performing (752) a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifiesthat, for a layer i, where i is an integer, the bitstream includes a setof first syntax element indicative of a first variable indicatingwhether the layer i is included in at least one of the plurality ofOLSs.

2. The method of solution 1, wherein the format rule specifies that, incase that, the first variable for the layer i is equal to zero, meaningthat the layer i is not included in any of the plurality of OLSs, thebitstream excludes a second set of syntax element indicative of decodedpicturebuffer parameters for the layer i.

3. The method of any of solutions 1-2, wherein the format rule furtherspecifies that the bitstream includes a third set of syntax element thatindicative of a second variable indicating whether the layer i is usedas a reference layer for at least one of the plurality of video layers,and wherein the format rule disallows the first variable and the secondvariable to have zero values.

4. The method of solution 3, wherein, wherein the format rule disallowsvalues of the first variable and the second variable are both equal to 0which indicates that no layer that is neither a direct reference layerof any other layer nor an output layer of at least one OLS.

5. The method of any of solutions 1-4, wherein the first variable is aone-bit flag, denoted as LayerUsedAsOutputLayerFlag.

6. The method of solution 5, wherein the first variable is determinedbased on iteratively checking, for each of the plurality of videolayers, a value of a third variable indicative of a relationship betweena number of layers included in the plurality of OLSs.

7. The method of solution 6, wherein the third variable indicative of arelationship between number of layers included in the plurality of OLSsis permitted to have a value 0, 1, or 2.

8. The method of any of solutions 1-7, wherein the performing theconversion comprising encoding the video into the bitstream; and themethod further comprises storing the bitstream in a non-transitorycomputer-readable recording medium.

9. A method for storing bitstream of a video, comprising: generating abitstream from the video comprising a plurality of video layers, andstoring the bitstream in a non-transitory computer-readable recordingmedium; wherein the bitstream comprises a plurality of output layer sets(OLSs), each of which comprises one or more of the plurality of videolayers, and the bitstream conforms to a format rule, wherein the formatrule specifies that, for a layer i, where i is an integer, the bitstreamincludes a set of first syntax element indicative of a first variableindicating whether the layer i is included in at least one of theplurality of OLSs.

For example, the following solutions may be implemented according toitem 4 in previous section.

1. A method of video processing (e.g., method 760 depicted in FIG. 7F),comprising performing (762) a conversion between a video and a bitstreamof the video, wherein the bitstream includes one or more output layersets each comprising one or more video layers; wherein the bitstreamconforms to a format rule, wherein the format rule specifies that anumber of decoded picture buffer parameter syntax structures included ina video parameter set for the bitstream is equal to: zero, in a casethat each output layer set includes a single video layer; or one plus avalue of a syntax element, in a case that each output layer set includesa single layer is not true.

2. The method of solution 1, wherein the syntax element corresponds to avps_num_dpb_params_minus1 syntax element.

3. The method of any of solutions 1-2, wherein the format rule specifiesthat, in case that another syntax element indicative of whether a samesize is used for indicating decoded picture buffer syntax structures forvideo layers that are included and not included in the one or moreoutput layer sets is absent in the video parameter set, a value of theanother syntax element is inferred to be equal to 1.

4. The method of any of solutions 1-3, wherein the performing theconversion comprises encoding the video into the bitstream; and themethod further comprises storing the bitstream in a non-transitorycomputer-readable recording medium.

5. A method for storing bitstream of a video, comprising: generating abitstream from the video; and storing the bitstream in a non-transitorycomputer-readable recording medium; wherein the bitstream includes oneor more output layer sets each comprising one or more video layers;wherein the bitstream conforms to a format rule, wherein the format rulespecifies that a number of decoded picture buffer parameter syntaxstructures included in a video parameter set for the bitstream is equalto: zero, in a case that each output layer set includes a single videolayer; or one plus a value of a syntax element, in a case that eachoutput layer set includes a single layer is not true.

For example, the following solutions may be implemented according toitem 7 in previous section.

1. A method of video processing (e.g., method 770 depicted in FIG. 7G),comprising performing (772) a conversion between a video and a bitstreamof the video, wherein the bitstream includes a coded video sequence(CVS) comprising one or more coded video pictures of one or more videolayers; and wherein the bitstream conforms to a format rule thatspecifies that one or more sequence parameter sets (SPS) indicative ofconversion parameters that are referred to by the one or more codedpictures of the CVS have a same reference video parameter set (VPS)identifier indicative of a referenced VPS.

2. The method of solution 1, wherein the format rule further specifiesthat the same reference VPS identifier has a value greater than 0.

3. The method of any of solutions 1-2 wherein the format rule furtherspecifies that a value zero for an SPS identifier is used in response toand only when the CVS comprises a single video layer.

4. The method of any of solutions 1-3, wherein the performing theconversion comprises encoding the video into the bitstream; and themethod further comprises storing the bitstream in a non-transitorycomputer-readable recording medium.

5. A method for storing bitstream of a video, comprising: generating abitstream from the video, and storing the bitstream in a non-transitorycomputer-readable recording medium; wherein the video comprises one ormore video pictures comprising one or more slices; wherein the bitstreamincludes a coded video sequence (CVS) comprising one or more coded videopictures of one or more video layers; and wherein the bitstream conformsto a format rule that specifies that one or more sequence parameter sets(SPS) indicative of conversion parameters that are referred to by theone or more coded pictures of the CVS have a same reference videoparameter set (VPS) identifier indicative of a referenced VPS.

For example, the following solutions may be implemented according toitem 8 in previous section.

1. A method of video processing (e.g., method 780 depicted in FIG. 7H),comprising performing (782) a conversion between a video and a bitstreamof the video, wherein the bitstream comprises one or more output layersets (OLSs) each comprising one or more video layers, wherein thebitstream conforms to a format rule; wherein the format rule specifieswhether or how a first syntax element indicating whether a first syntaxstructure descriptive of parameters of a hypothetical reference decoder(HRD) used for the conversion is included in a video parameter set (VPS)of the bitstream.

2. The method of solution 1, wherein the first syntax structurecomprises a set of general HRD parameters.

3. The method of solutions 1-2, wherein the format rule specifies thatthe first syntax element is omitted from the VPS and is inferred to havea zero value when not present in the VPS due to each of the one or morevideo layers being included in an OLS of the one or more OLSs, andwherein each of the one or more OLSs comprises a single video layer

4. The method of solutions 1-2, wherein the format rule specifies thatthe first syntax element has a zero value in the VPS when present in theVPS due to each of the one or more video layers being included in an OLSof the one or more OLSs, and wherein each of the one or more OLSscomprises a single video layer.

5. The method of any of solutions 1-4, wherein the format rule furtherspecifies whether or how a second syntax element indicative of a numberof syntax structures descriptive of OLS-specific HRD parameters isincluded in the VPS.

6. The method of solution 5, wherein the format rule further specifiesthat the second syntax element is included in the VPS when the firstsyntax element has a value 1, regardless of whether the total number ofOLSs in the one or more OLSs is greater than 1.

For example, the following solutions may be implemented according toitems 9, 10 in previous section.

7. A method of video processing (e.g., method 790 depicted in FIG. 7I),comprising performing (792) a conversion between a video and a bitstreamof the video, wherein the bitstream comprises one or more output layersets (OLSs) each comprising one or more video layers, wherein thebitstream conforms to a format rule; wherein the format rule specifieswhether or how a first syntax structure descriptive of generalhypothetical reference decoder (HRD) parameters and a number of secondsyntax structures descriptive of OLS-specific HRD parameters areincluded in a video parameter set (VPS) for the bitstream.

8. The method of solution 7, wherein the format rule specifies to omitthe first syntax structure from the VPS in case that no second syntaxstructure is included in the VPS.

9. The method of solution 7, wherein the format rule excludes inclusionof first syntax structure and the second syntax structures in the VPSfor an OLS comprising only one video layer, and wherein the format rulepermits inclusion of the first syntax structure and the second syntaxstructures an OLS comprising only one video layer.

10. A method for storing bitstream of a video, comprising: generating abitstream from the video; storing the bitstream in a non-transitorycomputer-readable recording medium; wherein the bitstream comprises oneor more output layer sets (OLSs) each comprising one or more videolayers, wherein the bitstream conforms to a format rule; wherein theformat rule specifies whether or how a first syntax element indicatingwhether a first syntax structure descriptive of parameters of ahypothetical reference decoder (HRD) used for the conversion is includedin a video parameter set (VPS) of the bitstream.

The above-listed solutions may further include:

In some embodiments, in the above-listed solutions, the performing theconversion comprising encoding the video into the bitstream.

In some embodiments, in the above-listed solutions, the performing theconversion comprises parsing and decoding the video from the bitstream.

In some embodiments, in the above-listed solutions, the performing theconversion comprises encoding the video into the bitstream; and themethod further comprises storing the bitstream in a non-transitorycomputer-readable recording medium.

In some embodiments, a video decoding apparatus includes a processorconfigured to implement a method recited in one or more of above-listedsolutions.

In some embodiments, a video encoding apparatus includes a processorconfigured to implement a method recited in one or more of above-listedsolutions.

In some embodiments, a non-transitory computer-readable storage mediummay store instructions that cause a processor to implement a methodrecited in one or more of above-listed solutions.

In some embodiments, a non-transitory computer-readable recording mediumstoring a bitstream of a video which is generated by a method recited inone or more of above-listed solutions.

In some embodiments, the above-described encoding methods may beimplemented by an apparatus and the apparatus may further write abitstream generated by implementing the method to a computer-readablemedium.

The disclosed and other solutions, examples, embodiments, modules andthe functional operations described in this document can be implementedin digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this document and theirstructural equivalents, or in combinations of one or more of them. Thedisclosed and other embodiments can be implemented as one or morecomputer program products, i.e., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them. A propagated signal is anartificially generated signal, e.g, a machine-generated electrical,optical, or electromagnetic signal, that is generated to encodeinformation for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any subject matter or of whatmay be claimed, but rather as descriptions of features that may bespecific to particular embodiments of particular techniques. Certainfeatures that are described in this patent document in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to a subcombination or variation of a sub combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

The invention claimed is:
 1. A method of video processing, comprising:performing a conversion between a video comprising a plurality of videolayers and a bitstream of the video, wherein the bitstream comprises aplurality of output layer sets (OLSs), each of which comprises one ormore of the plurality of video layers, and the bitstream conforms to aformat rule, wherein the format rule specifies that, for a layer i,where i is an integer, the bitstream includes a set of first syntaxelements which is used to derive a first variable indicating whether thelayer i is used as an output layer in at least one of the plurality ofOLSs, wherein the format rule further specifies that the bitstreamincludes a set of third syntax elements which is used to derive a secondvariable indicating whether the layer i is used as a reference layer forat least one of the plurality of video layers, and wherein the formatrule disallows values of the first variable and the second variable bothequal to 0, and wherein disallowing the values of the first variable andthe second variable both equal to 0 indicates that no layer that isneither a direct reference layer of any other layer nor an output layerof at least one OLS.
 2. The method of claim 1, wherein the format rulespecifies that, the first variable for the layer i is equal to zero,meaning that the layer i is not used as an output layer in any of theplurality of OLSs.
 3. The method of claim 2, wherein the format rulespecifies that, in case that the first variable for the layer i is equalto zero, the bitstream excludes a set of second syntax elementsindicative of decoded picture buffer parameters for the layer i.
 4. Themethod of claim 1, wherein the first variable is a one-bit flag, denotedas LayerUsedAsOutputLayerFlag.
 5. The method of claim 1, wherein thefirst variable is determined based on iteratively checking, for each ofthe plurality of video layers, a value of a third variable indicative ofa relationship between the plurality of video layers and the pluralityof OLSs.
 6. The method of claim 1, wherein the performing the conversioncomprises encoding the video into the bitstream.
 7. The method of claim1, wherein the performing the conversion comprises decoding the videofrom the bitstream.
 8. An apparatus for processing video data comprisinga processor and a non-transitory memory with instructions thereon,wherein the instructions upon execution by the processor, cause theprocessor to: perform a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifiesthat, for a layer i, where i is an integer, the bitstream includes a setof first syntax elements which is used to derive a first variableindicating whether the layer i is used as an output layer in at leastone of the plurality of OLSs, wherein the format rule further specifiesthat the bitstream includes a set of third syntax elements which is usedto derive a second variable indicating whether the layer i is used as areference layer for at least one of the plurality of video layers, andwherein the format rule disallows values of the first variable and thesecond variable both equal to 0, and wherein disallowing the values ofthe first variable and the second variable both equal to 0 indicatesthat no layer that is neither a direct reference layer of any otherlayer nor an output layer of at least one OLS.
 9. The apparatus of claim8, wherein the format rule specifies that, the first variable for thelayer i is equal to zero, meaning that the layer i is not used as anoutput layer in any of the plurality of OLSs.
 10. The apparatus of claim8, wherein the first variable is a one-bit flag, denoted asLayerUsedAsOutputLayerFlag.
 11. The apparatus of claim 8, wherein thefirst variable is determined based on iteratively checking, for each ofthe plurality of video layers, a value of a third variable indicative ofa relationship between the plurality of video layers and the pluralityof OLSs.
 12. The apparatus of claim 8, wherein the performing theconversion comprises encoding the video into the bitstream, and theapparatus is an encoder.
 13. The apparatus of claim 8, wherein theperforming the conversion comprises decoding the video from thebitstream, and the apparatus is a decoder.
 14. A non-transitorycomputer-readable storage medium storing instructions that cause aprocessor to: perform a conversion between a video comprising aplurality of video layers and a bitstream of the video, wherein thebitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifiesthat, for a layer i, where i is an integer, the bitstream includes a setof first syntax elements which is used to derive a first variableindicating whether the layer i is used as an output layer in at leastone of the plurality of OLSs, wherein the format rule further specifiesthat the bitstream includes a set of third syntax elements which is usedto derive a second variable indicating whether the layer i is used as areference layer for at least one of the plurality of video layers, andwherein the format rule disallows values of the first variable and thesecond variable both equal to 0, and wherein disallowing the values ofthe first variable and the second variable both equal to 0 indicatesthat no layer that is neither a direct reference layer of any otherlayer nor an output layer of at least one OLS.
 15. The non-transitorycomputer-readable storage medium of claim 14, wherein the format rulespecifies that, the first variable for the layer i is equal to zero,meaning that the layer i is not used as an output layer in any of theplurality of OLSs.
 16. The non-transitory computer-readable storagemedium of claim 14, wherein the first variable is a one-bit flag,denoted as LayerUsedAsOutputLayerFlag.
 17. The non-transitorycomputer-readable storage medium of claim 14, wherein the first variableis determined based on iteratively checking, for each of the pluralityof video layers, a value of a third variable indicative of arelationship between the plurality of video layers and the plurality ofOLSs.
 18. A non-transitory computer-readable recording medium storing abitstream of a video which is generated by a method performed by a videoprocessing apparatus, wherein the method comprises: generating thebitstream of the video comprising a plurality of video layers, whereinthe bitstream comprises a plurality of output layer sets (OLSs), each ofwhich comprises one or more of the plurality of video layers, and thebitstream conforms to a format rule, wherein the format rule specifiesthat, for a layer i, where i is an integer, the bitstream includes a setof first syntax elements which is used to derive a first variableindicating whether the layer i is used as an output layer in at leastone of the plurality of OLSs, wherein the format rule further specifiesthat the bitstream includes a set of third syntax elements which is usedto derive a second variable indicating whether the layer i is used as areference layer for at least one of the plurality of video layers, andwherein the format rule disallows values of the first variable and thesecond variable both equal to 0, and wherein disallowing the values ofthe first variable and the second variable both equal to 0 indicatesthat no layer that is neither a direct reference layer of any otherlayer nor an output layer of at least one OLS.
 19. The non-transitorycomputer-readable recording medium of claim 18, wherein the format rulespecifies that, the first variable for the layer i is equal to zero,meaning that the layer i is not used as an output layer in any of theplurality of OLSs and wherein the first variable is a one-bit flag,denoted as LayerUsedAsOutputLayerFlag.
 20. The non-transitorycomputer-readable recording medium of claim 18, wherein the firstvariable is determined based on iteratively checking, for each of theplurality of video layers, a value of a third variable indicative of arelationship between the plurality of video layers and the plurality ofOLSs.